Crafting Urban Landscapes and Monumental Infrastructure: Archaeometric Investigations of White Marble Architectural Elements from Roman Philippopolis (Bulgaria)

Abstract

This study explores the provenance of white marble architectural elements from Roman Philippopolis, with a particular focus on the Eastern Gate complex. By determining the origin of the marble, we aim to elucidate economic, social, and urban dynamics related to material selection and trade networks. The investigation examines the symbolic significance of prestigious marble in elite representation and highlights the role of quarry exploitation in the region’s economic and technological development. The Eastern Gate, a monumental ensemble integrated into the city’s urban fabric, was primarily constructed with local Rhodope marble, alongside imported materials such as Prokonnesian marble. Analytical methods included petrographic examination, chemical analysis of trace elements (Mn, Mg, Fe, Sr, Y, V, Cd, La, Ce, Yb, and U), and stable isotope analysis (δ¹⁸O, δ¹³C). Statistical evaluations were performed for each sample (37 in total) and compared with a comprehensive database of ancient quarry sources. The results underscore the dominance of local materials while also indicating selective use of imports, potentially linked to symbolic or functional criteria. The findings support the hypothesis of local workshop activity in the Asenovgrad/Philippopolis area and shed light on regional and long-distance marble trade during the Roman Imperial period, reflecting broader economic and cultural interconnections.

1. Introduction

As early as the founding of the Roman province of Thrace, Philippopolis began to gain an economic advantage due to its location near major trade routes, which provided it with strategic control and access to various goods (local and imported) [1] (Figure 1). The city gained the name of the metropolis under the reign of Domitian and kept the title throughout most of Antiquity. This status conferred the authority to mint coins, leading to significant political and economic advancement for the city. Concurrently, the city undertook extensive construction projects and urban development, which contributed to its overall growth [2]. Given its central location within the province, the urban development of Philippopolis is likely to have significantly influenced the overall process of urbanisation in Thrace [3]. Roman Philippopolis preserves a fortification system, an orthogonal street network, and various civil and public buildings. Well-preserved ruins are also identified as the theatre and the stadium [4].

The city’s architectural landscape experienced considerable enhancement through the assimilation and reinterpretation of architectural decorative models that enjoyed widespread popularity throughout the empire [3] (The resemblance between the arch in Philippopolis and its counterpart in Gerasa (located in present-day northern Jordan), encompassing dating and positioning within the urban context, strongly indicates their inclusion in analogous construction initiatives, contributing to the delineation of the urban framework [5].). Philippopolis’ architectural embellishment adhered to established standards for architectural decoration set by leading stonemasonry workshops in the Roman Empire, including Attica, Ephesos, Pergamon, and Aphrodisias. The developmental phases of the architectural orders and their integration into the city’s urban fabric signify a prolonged transformation process, seemingly synchronised with pivotal periods of urban expansion [6] (It is noteworthy that the principal characteristics of the Corinthian order employed in the architecture of Philippopolis, albeit with minor modifications, can be compellingly dated to the same period as the prototype patterns originating from Ephesos, Pergamum, Aphrodisias, Athens, and Corinth [6].). The urban landscape of the city is adorned with numerous architectural features and design patterns, showcasing the exceptional quality and artistic characteristics influenced by renowned stonemason workshops across the Roman Empire. Incorporating Anatolian decorative models, particularly in handling essential elements of the five architectural orders, invites us to delve beyond mere identification of architectural style and craftsmanship. This exploration prompts consideration of the use of imported stone material from quarries beyond Thrace’s borders, reflecting the province’s economic development and unveiling cultural influences on the continuous evolution of the urban environment [3].

Recent scholarship has increasingly highlighted how architectural choices and urban planning in provincial cities were shaped by complex interactions between local traditions, imperial models, and evolving economic networks. In particular, the selective use of imported building materials such as marble can be read as a material expression of civic identity, elite ambition, and participation in broader imperial dynamics. For a wider discussion of evolving urban landscapes in Roman provincial contexts, see [7,8,9,10,11,12].

2. The Case Study of the Eastern Gate

The Eastern Gate of Philippopolis complex, located at the eastern foot of the Three Hills, consists of an honorary arch, dated to the reign of Emperor Hadrian; a fortification wall with a gate, dated to the reign of Emperor Marcus Aurelius; a fortification wall with a gate and a colonnaded street from the beginning of the fourth century AD; and additional buildings of still unclear type and chronology (Figure 2a,b). The start of the construction of the complex is dated to the beginning of the second century AD, with the completion of the alterations in Late Antiquity [13]. Based on current studies, the earliest archaeological structure is an honorary arch with a Hadrianic date, which predates the city walls. The arch was later incorporated into the city’s Eastern Gate, so its structure and elevation are still not entirely clear. It is known that the two pillars of the arch were built in opus quadratum of sandstone blocks covered with marble slabs, over a profiled base. The decoration of the honorary arch was particularly distinguished by the intricate designs on the pilasters and pilaster capitals, made in white marble. Based on the decorative characteristics of the architectural elements, the construction has been dated to the 120s or the beginning of the 130s [5,6,14]. In AD 172, the honorary arch remained outside the fortified city, when a fortification wall with a gate was built south of it. A bilingual building inscription (IGBulg III, 1, 878) [15], which once stood on the wall, states that the new fortification system of Philippopolis was built by (or with funding from) Emperor Marcus Aurelius (The large-scale building campaign of Marcus Aurelius aimed to protect the cities of Thrace from the attacks of the Marcomanni and Costoboci [14].). The next building campaign on the territory of the complex was carried out after the devastation of the city by the Goths in the middle of the third century AD. At the beginning of the fourth century AD, a completely new fortification wall with a triple-arched gate (the Eastern Gate) and a monumental street with sidewalks and porticoes was constructed. At the end of the century or the beginning of the next, the gate was reinforced with two rectangular towers. The street from the gate leading to the city, which was decorated with colonnades on both sides, appears to have been the largest in Philippopolis, with a width of 13.20 m [16] (Figure 2a,b). The architectural elements of the Corinthian order in the colonnades, however, can be dated to the Severan period, which indicates their reuse in the porticoes along the street [14].

This study examines the use of both local and imported marble in architectural artefacts, investigating its roles in structural elements and decoration through archaeometric studies of white marble provenance. A key focus is determining the criteria influencing these material choices, whether aesthetic, functional, or economic. Additionally, the research investigates the development of the stone trade and the extent of Thrace’s connections with regional and supra-regional marble quarries, including those of Thasos, Prokonnesos, etc. By analysing these trade networks, the study aims to shed light on the economic and cultural interactions that shaped the material landscape of the region.

The Sampled Artefacts

A total of thirty-seven architectural elements of the Eastern gate were sampled and investigated. This representative group includes pedestals, column shafts, pilasters, Corinthian columns and pilaster capitals, frieze-architraves, archivolts, cornices, stylobate blocks, a block used as a door frame, and a monumental relief. Two statue bases (FWM0365; FWM0431) found at the site of the Eastern gate were also analysed, as well as a frieze-architrave depicting a gladiatorial battle (FWM0559), which was used here as spolia (

Table 1. The sampled artefacts (ed. by V. Anevlavi, P. Dakasheva, and P. Andreeva).

Lab Nr	Project Nr	M. Nr	Object	Material	Marble Description	Dating	Location	Find Spot	Details on Finding Spot	Provenance Results	Photo	Bibliography
9722	FWM0364	n/a	Frieze-architrave	Marble	White colour; coarse-grained with fine matrix, grey specks	First half of the second century AD, probably Hadrianic period	In situ	Plovdiv	Eastern gate	Asenovgrad		[18], p. 32; [15], p. 166
Description: Fragment of a frieze-architrave block with a Greek inscription. The architrave is divided into three protruding fasciae, and the inscription (AYTO) is incised on the uppermost fascia. The moulding between the architrave and the frieze, and the decoration of the frieze itself, are not preserved.
9723	FWM0365	101	Statue base	Marble	White colour; coarse-grained; ultra-fine layers	First half of the third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[15], p. 180
Description: With a Greek inscription. The lower part of the pedestal is broken off. The moulding of the upper part is adorned with stylised acroteria.
9724	FWM0366	n/a	Pedestal	Marble	White colour; coarse-grained with fine-grained veins	Hadrianic period	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: Part of one of the pillars of the honorary arch. Parallelepiped shape, smooth surface, and profiled upper and lower end. The pedestal stands on a profiled plinth.
9725	FWM0367	n/a	Pilaster	Marble	White/beige colour; coarse-grained with fine-grained veins	Hadrianic period	In situ	Plovdiv	Eastern gate	Asenovgrad		[6,14]
Description: From the honorary arch, used as spolia in the Late Antique gate. Corner pilaster with two adjacent decorated sides, of which only one is preserved and visible today. The front side is surrounded by a profiled frame, in the centre of which there is relief decoration of acanthus scrolls. The moulding of the frame consists of bead-and-reel and leaf-and-dart.
9726	FWM0368	n/a	Block	Marble	White colour; coarse-grained with fine-grained veins	Second to third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		n/a
Description: Used as a door frame. Block with parallelepiped shape, without decoration. The upper part is broken off.
9727	FWM0369	n/a	Block	Marble	White colour; coarse-grained with fine-grained veins	Second to third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: From the northern stylobate of the colonnade along the street. The block has a parallelepiped shape.
9728	FWM0370	n/a	Block	Marble	White colour; coarse-grained with fine-grained veins	Second to third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: From the northern stylobate of the colonnade along the street. The block has a parallelepiped shape.
9729	FWM0371	n/a	Block	Marble	White colour; coarse-grained with fine-grained veins	Second to third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: From the northern stylobate of the colonnade along the street. The block has a parallelepiped shape.
9730	FWM0372	n/a	Block with unfinished decoration	Marble	White colour; coarse-grained with fine-grained veins	End of the second to the first decades of the third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		n/a
Description: Reused in the northern stylobate of the colonnade along the street. The block has a parallelepiped shape. At the upper left end of the block, there is a horizontal decoration of egg-and-dart.
9731	FWM0373	2	Corinthian column capital	Marble	White/brownish/beige/greyish colour; coarse-grained	Middle to second half of the second century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[5,6]
Description: Normal Corinthian capital, Asiatic type. The helices are shaped differently. Three of the abacus flowers and three of the corners of the abacus with the adjacent volutes are broken off.
9732	FWM0374	3	Corinthian column capital	Marble	White colour; coarse-grained	Severan period	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: Corinthian capital, Asiatic type. There are no helices. Three of the corners of the abacus with the adjacent volutes are broken off.
9733	FWM0375	42	Corinthian column capital	Marble	White colour; coarse-grained	Severan period	In situ	Plovdiv	Eastern gate	Prokonnesos		[14]
Description: Corinthian capital, Asiatic type. There are no helices. Two of the corners of the abacus with the adjacent volutes are broken off.
9734	FWM0376	43	Corinthian column capital	Marble	White colour; fine to medium-grained	Severan period	In situ	Plovdiv	Eastern gate	Prokonnesos		[6,14]
Description: Normal Corinthian capital, Asiatic type. There are helices on one side of the capital. All corners of the abacus with the adjacent volutes are broken off.
9735	FWM0377	44	Corinthian column capital	Marble	White colour with grey layers; fine to medium-grained	Severan period	In situ	Plovdiv	Eastern gate	Prokonnesos		[14,19]
Description: Corinthian capital, Asiatic type. There are no helices. All corners of the abacus with the adjacent volutes are broken off.
9736	FWM0378	13	Shaft	Marble	White colour; fine/coarse-grained	Second to the first decades of the third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: Part of a shaft of a free-standing column with a smooth, polished surface.
9737	FWM0379	27	Shaft	Marble	White colour; fine-grained	Second to the first decades of the third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: Upper part of a shaft of a free-standing column with a smooth, polished surface. The neck of the shaft is preserved.
9738	FWM0380	27	Shaft	Marble	White/beige colour; coarse-grained	Second to the first decades of the third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: Upper part of a shaft of a free-standing column with a smooth polished surface. The neck of the shaft is preserved.
9739	FWM0381	38	Shaft	Marble	White colour; medium to coarse-grained	Second to the first decades of the third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: Monolithic shaft of a free-standing column with a smooth polished surface.
9740	FWM0382	52	Cornice with consoles	Marble	White colour; coarse-grained with fine-grained veins	Severan period	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: The mouldings consist of dentils, egg-and-dart, leaf-and-dart, consoles with acanthus leaves and coffers, bead-and-reel, and sima decorated with palmette anthemion.
9741	FWM0383	57	Cornice with consoles	Marble	White colour; coarse-grained with fine-grained veins	Severan period	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: The mouldings consist of dentils, egg-and-dart, leaf-and-dart, consoles with acanthus leaves and coffers, bead-and-reel, and sima decorated with palmette anthemion.
9742	FWM0384	85	Cornice with consoles	Marble	White colour; coarse-grained with fine-grained veins	Severan period	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: The mouldings consist of dentils, egg-and-dart, leaf-and-dart, consoles with acanthus leaves and coffers, bead-and-reel, and sima decorated with palmette anthemion.
9743	FWM0385	94	Cornice with consoles	Marble	White colour; coarse-grained with fine-grained veins	Severan period	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: The mouldings consist of dentils, egg-and-dart, leaf-and-dart, consoles with acanthus leaves and coffers, bead-and-reel, and sima decorated with palmette anthemion.
9744	FWM0386	60	Pedestal	Marble	White colour; coarse-grained with fine-grained veins	Second half of the second -beginning of the third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: Part of a pedestal made of a monolithic block together with an Attic-Ionic base for a free-standing column. The lower part is missing. At a later stage, a round hole was drilled just below the upper moulding of the pedestal.
9745	FWM0387	48	Pedestal	Marble	White colour; coarse-grained with a fine matrix	Second half of the second to the first decades of the third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: Part of a pedestal made of a monolithic block together with an Attic-Ionic base for a free-standing column. The lower moulding is broken off.
9746	FWM0388	80	Frieze-architrave	Marble	White colour; coarse-grained with fine-grained veins	Severan period	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: Block turned upside down. The architrave on the posterior side is divided into three protruding fasciae. Beds for beams are formed above it. The soffit is decorated with a plant motif.
9747	FWM0389	87	Frieze-architrave	Marble	White colour; coarse-grained with fine-grained veins	Severan period	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: The architrave on the posterior side is divided into three protruding fasciae. Beds for beams are formed above it. The soffit is decorated with a plant motif.
9748	FWM0390	40	Frieze-architrave	Marble	White colour; coarse-grained with fine-grained veins	Hadrianic period	In situ	Plovdiv	Eastern gate	Asenovgrad		[6]
Description: The architrave was divided into three protruding fasciae, the lowest of which is missing. There is a bead-and-reel above each fascia. The finishing moulding of the architrave features a leaf-and-dart motif. The frieze is decorated with bullheads and garlands. There are rosettes above the garlands. The upper end of the block is decorated with egg-and-tongue (or dart).
9749	FWM0391	6	Cornice with consoles	Marble	White colour; coarse-grained with fine-grained veins	Late-Hadrianic period	In situ	Plovdiv	Eastern gate	Asenovgrad		[6]
Description: The main mouldings consist of dentils, consoles with acanthus leaves and coffers, and sima decorated with palmette anthemion. The coffers are framed with bead-and-reel and egg-and-tongue.
9750	FWM0392	4	Corinthian pilaster capital	Marble	White colour; coarse-grained	Hadrianic period	In situ	Plovdiv	Eastern gate	Asenovgrad		[6]
Description: From the honorary arch, above a corner pilaster with two adjacent decorated sides. The capital has a cubic shape, due to which its decorative elements are reduced, namely, the number of acanthus leaves arranged in one row only. The acanthus leaves are of Asiatic type and the helices of Attic type.
9751	FWM0393	5	Block with shell decoration	Marble	White colour; coarse-grained	Second century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[15]
Description: Part of a blind niche or water basin decorated with a shell motif.
9752	FWM0394	48	Pedestal	Marble	White colour; coarse-grained with fine-grained veins	Second half of the second to the first decades of the third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		[14]
Description: The upper part is broken off. It is possible that the pedestal was made of a monolithic block together with an Attic-Ionic base (?).
9753	FWM0395	19	Corinthian column capital	Marble	White colour; coarse-grained	Severan period	In situ	Plovdiv	Eastern gate	Prokonnesos		[14]
Description: Corinthian capital, Asiatic type. There are no helices. One of the abacus flowers is replaced by an eagle. The capital is split in two and all corners of the abacus with the adjacent volutes are broken off.
9754	FWM0396	39	Block	Marble	White colour; coarse-grained with fine-grained veins	End of the second to the first decades of the third century AD	In situ	Plovdiv	Eastern gate	Asenovgrad		n/a
Description: Form of an arch or vault. The curved moulded part (archivolt) is divided into three protruding fasciae, which end with leaf-and-dart. Above the lower fascia, there is a twisted rope ornament, and above the next two, bead-and-reel. There is a horizontal decoration of egg-and-dart above the archivolt.
9755	FWM0397	18	Block	Marble	White colour; fine-grained in a coarse matrix	Hadrianic period (?)	In situ	Plovdiv	Eastern gate	Asenovgrad		[5]
Description: From a vault, possibly a blind niche. The front curved part (archivolt) is divided into three protruding fasciae. There are no additional ornaments, and the moulding at the upper end is broken off.
9756	FWM0398	301	Frieze-architrave	Marble	White colour; fine-grained in a coarse matrix	Severan period	In situ	Plovdiv	Eastern gate	Asenovgrad		[15]
Description: The architrave is divided into three protruding fasciae. Above the lower fascia there is a twisted rope ornament, and above the next two, bead-and-reel. The finishing moulding of the architrave features a leaf-and-dart motif. The unadorned frieze has a convex profile. The upper end of the block is decorated with egg-and-dart. The soffit is decorated with a wave motif.
9786	FWM0431	n/a	Statue base	Marble	White colour; medium to coarse-grained	First half of the third century AD	Plovdiv Depot	Plovdiv	Eastern gate	Asenovgrad		[15], pp. 160–164
Description: With a Greek inscription. Severely damaged.
9787	FWM0432	201	Corinthian column capital	Marble	Greyish colour; medium to coarse-grained	Severan period	Plovdiv Depot	Plovdiv	Eastern gate	Prokonnesos		[15]
Description: Normal Corinthian capital, Asiatic type. There are palmette helices on at least one side. One of the abacus flowers is replaced by an eagle. All corners of the abacus with the adjacent volutes are broken off.
9788	FWM0433	n/a	Corinthian column capital	Marble	Greyish colour and grey banding; medium-grained	Severan period	Plovdiv Depot	Plovdiv	Eastern gate	Prokonnesos		n/a
Description: Normal Corinthian capital, Asiatic type. There are palmette helices on at least one side. One of the abacus flowers is replaced by an eagle. All corners of the abacus with the adjacent volutes are broken off.
9789	FWM0434	1021	Monumental relief	Marble	White colour; fine-grained, partly medium-grained	Second half of the second century AD	Regional Archaeological Museum Plovdiv (RAMP)	Plovdiv	Eastern gate	Asenovgrad		[20], p. 238
Description: Corner block with figural decoration and an embossed frame on the top and bottom. The relief decoration consists of two corner images and eight human figures between them (including the gods Asclepius, Hygeia, and Telesphorus).

Dating of the artefacts is based on information from the published literature (see references indicated in the table). All provenance determinations in this table are based on the present study’s archaeometric analysis (combining petrographic, stable isotope, and trace element data), as described in the Methods Section 3. Samples FWM0379 and FWM0380 originate from the same column shaft but were taken from different locations with varying grain sizes. Analysis revealed that despite the differences in grain size, the geochemical signatures of both samples are identical.

) (Remarks on grain sizes are as follows: 0.5–1.2 mm—fine grain; 1.2–2.5 mm—medium grain; >2.5 mm—coarse grain [17].).

3. Archaeometric Methodology

Recent systematic research has uncovered numerous ancient quarries of white and whitish marbles, broadening the scope of studies and allowing for new hypotheses regarding the utilisation and distribution of marble across different historical periods. Consequently, this has necessitated refinements in research methodologies, the development of comprehensive databases, and the improvement of techniques for distinguishing between different marble sources.

A comparison was conducted between archaeological samples and a database consisting of 5700 geological samples from marble quarries and outcrops of the ancient world, including sources such as Aphrodisias, Carrara, Prokonnesos, Dokimeion, Penteli, Paros, Thasos, Heraklea/Miletos, and Ephesos, as well as marble sources from Roman Macedonia and Thrace [17,21,22,23,24,25,26]. Additionally, samples from surrounding locations relevant to each group were incorporated into the study (The database has been compiled from various studies over the last 20 years by Walter Prochaska (author) from the University of Leoben in collaboration with the Austrian Archaeological Institute in Vienna. The specimens are sorted in the repositories of the Austrian Archaeological Institute of the Austrian Academy of Sciences.). The final selection of quarries that exhibited the closest geochemical similarities with the analysed archaeological specimens is presented in the following diagrams. Analytical heterogeneity and the extensive number of quarries and sources of marble production in antiquity necessitate a multi-method approach for accurate provenance analysis. After the measurements are completed, statistical analyses are applied to the results, which are then cross-referenced with the databases to determine the provenance of each sample.

Microscopy: Due to the inherent textural variability of marble, even within a single quarry, petrographic features have limited applicability in provenance analysis [27,28]. However, distinct petrographic differences among the marble groups examined in this study enable an initial classification into broader categories. The mineralogical identification of the carbonate phase was conducted using optical microscopy on thin sections under cross-polarised and plane-polarised light. The observed optical properties—such as high birefringence, rhombohedral cleavage, characteristic twinning, and lack of features typical of dolomite—support the identification of calcite. In addition, the geochemical results (trace element patterns and isotopic values) are entirely consistent with a calcitic composition and show no indications of a significant dolomitic component (While no X-ray diffraction (XRD) or Raman spectroscopy was performed on these samples, the combined petrographic and geochemical data provide a robust and accurate basis for determining the carbonate mineral type within the context of this study.).

Stable Isotope Analysis: The analysis of stable isotopes of oxygen (O) and carbon (C) is a widely accepted method for determining the provenance of marble and is offered by several specialised laboratories. This technique is considered reliable; however, it must be applied cautiously, particularly when dealing with weathered or contaminated surfaces, as these factors can impact the accuracy of the results [29,30].

Trace Element Analysis: In this study, a broad range of trace elements was analysed using ICP-MS (Inductively Coupled Plasma Mass Spectrometry) following the dissolution of the carbonate phase exclusively with hot nitric acid (HNO₃). This approach ensures that silicates remain undissolved. Therefore, it is crucial to avoid comparing or combining these trace element data with results obtained through bulk analytical methods such as HF dissolution or XRF analysis. This is because bulk methods measure the combined composition of carbonate and non-carbonate phases, whereas selective HNO₃ dissolution provides trace element data specific to the carbonate fraction, which is essential for accurate marble provenance discrimination [31]. Since many important trace elements in marble—including Mn, Mg, Fe, Sr, Y, V, Cd, Ba, La, Ce, Yb, and U—occur only at sub-ppm levels, extreme diligence must be exercised in both sample preparation and analysis execution (The data include the stable isotopic values of carbon and oxygen, as well as the chemical values from the ICP-MS analysis, including magnesium, manganese, iron, strontium, chromium, vanadium, yttrium, cadmium, boron, lanthanum, cerium, praseodymium, dysprosium, holmium, ytterbium, lead, and uranium (data in ppm). The statistical programs used for analysis are STATISTICA and SPSS.) [5,32,33,34].

The analytical methods applied in these investigations were presented in detail in [23,24,25].

4. Provenance Results

4.1. Petrographic Data

To ensure the preservation of the objects, we sampled only a small portion of each, approximately 2 g. Consequently, petrographic analysis was conducted on a limited number of thin sections derived from selected architectural elements (five in total). While these petrographic results represent a small subset of the overall dataset, they provide a valuable initial grouping of the artefacts that can be further evaluated through isotopic and geochemical analyses. The limited number of thin sections does not compromise the reliability or quality of the forthcoming geochemical results, which are based on a broader and more representative sampling. Petrographic analyses were carried out using a petrographic microscope, with samples prepared as thin sections and examined under a Kern OPO 185 microscope. Comparative assessments were based on the thin section reference collection established by Prof. Prochaska (ÖAI/ÖAW), comprising approximately 350 geological samples sourced from both ancient and modern quarries and housed at the Austrian Archaeological Institute. Representative examples of comparative thin sections are published in [24], while additional petrographic data specifically concerning Asenovgrad marble artefacts can be found in [34].

Each thin section was systematically examined and documented, focusing on characteristics such as grain size, mineral composition, and observable structures or alterations. The detailed descriptions provided a comprehensive analysis of the mineralogical, textural, and structural features present within the thin sections. Detailed photographs of each thin section were meticulously captured to provide valuable visual representations of the intricate mineralogical and structural features. The use of cross-polarised light emphasised mineralogical variations, grain boundaries, and potential deformational structures within the samples, enhancing the clarity of these characteristics.

The final architectural element group analyses belong to the Eastern gate (FWM0373; FWM0374; FWM0375; FWM0378; FWM0392). As expected, after studying the previous architectural blocks, the majority of this building’s samples indicate Rhodope sources, characterised by medium to coarse-grained size, heteroblastic texture, opaque minerals, and mica as inclusions, as well as deformed twin lamellae (slightly curved). A particular sample, FWM0378, is separated into three parts: low, middle, and upper. The lower part is ultra-mylonitic, characterised by the absence of larger crystals, the central part contains many larger crystals within a fine matrix, and the upper part features a fine matrix with a few scattered larger crystals. Undulose extinction can also be observed. One sample (FWM0375) differentiates from the other artefacts with medium-grained size, heteroblastic texture, straight twin lamellae, and curved grain boundaries. This calcite marble is relatively pure with low amounts of trace minerals (

Table 2. The mineralogical characteristics of the sampled artefacts (ed. by V. Anevlavi; ÖAI/ÖAW).

Sample Nr	Type	Grain Size			Texture		Fabric Features		Accessory Minerals	Other Observations
		Fine	Medium	Coarse	Heteroblastic	Homeoblastic	Mosaic, Mortar, Lineated	Straight, Curved, Sutured
FWM0373	calcite		x		x		mortar	sutured	opaque minerals; mica	deformed twin lamellae—slightly curved; smaller grains and fluid inclusions along the schistosity
FWM0374	calcite		x		x		mortar	sutured	opaque minerals; mica	deformed twin lamellae—slightly curved; larger relics (with corroded surroundings)
FWM0375	calcite		x		x		mortar	curved	n.a.	straight twin lamellae
FWM0378	calcite	x			x		mosaic mainly/ partly mortar	sutured	opaque minerals; quartz (at the lower part)	deformed twin lamellae—slightly curved; the sample is separated into three parts, low, middle, and upper; the lower part is ultra-mylonitic with no larger crystals; the middle part has many larger crystals between the fine matrix; the upper part has a fine matrix with few scattered larger crystals; undulose extinction
FWM0392	calcite			x	x		mortar	sutured	opaque minerals; many mica inclusions; quartz	deformed twin lamellae—slightly curved

and

Table 3. The sampled artefacts under cross-polarised and transmitted light (ed. by V. Anevlavi; ÖAI/ÖAW).

Sample Nr	Polarised Light Photos	Transmitted Light Photos
FWM0373
FWM0374
FWM0375
FWM0378
FWM0392

).

While petrographic thin sections were prepared for five representative samples, the provenance determination for all 37 sampled architectural elements is based on trace element (ICP-MS) and stable isotope analysis, supported by multivariate statistical comparison with an extensive reference database (see below).

4.2. Geochemical Data

To manage the complexity of integrating multiple geochemical variables, this study adopted a systematic and statistically robust approach. Stable isotope data and trace element concentrations were analysed through a structured workflow grounded in established multivariate methods. Discriminant analysis was performed using both STATISTICA and SPSS, widely recognised tools in archaeometric research [17,34]. SPSS was used to compute discriminant functions, assigning each sample probabilistically to a quarry group based on its geochemical signature, while STATISTICA provided synthetic discriminant factors that visualise clustering patterns. These graphical outputs offer an effective means of assessing geochemical matches between archaeological artefacts and reference materials. A consistent set of variables (see Table S1) was applied throughout to ensure methodological coherence and comparability with the reference database. The resulting classification model is both statistically rigorous and reproducible, providing a reliable basis for provenance attribution and minimising the potential for subjective interpretation.

Isotopic and multivariate diagrams indicate the preliminary results by connecting the artefacts with two main sources. The isotope diagram is inconclusive since multiple sources overlap with each other (Figure 3). The multivariate diagram provides better discrimination by using the variables Mg, Fe, Mn, Sr, Cr, V, Y, Yb, Ba, Cd, La, Ce, U, δ¹⁸O‰, and δ¹³C‰ (Figure 4). The results of the architectural elements of the Eastern gate showed the use of marble from Asenovgrad and Prokonnesos. One sample (FWM0377) appears to be of Thasian origin. For calculating the degree of discrimination, the SPSS programme was used, applying the same variables as in the STATISTICA programme (Table S1).

According to statistical discrimination, the sample FWM0377 is linked to the Prokonnesian quarries, despite its placement on the multivariate diagram within the Thasian ellipse. This result aligns with the macroscopic description of the medium-grained size, white colour, and grey banding. This result compiles the Prokonnesian group with a total of six objects (FWM0375; FWM0376; FWM0432; FWM0433; FWM0495) (

Table 4. The calculated statistical parameters of the investigated marble samples. Variables used are as follows: Mg, Fe, Mn, Sr, Cr, V, Y, Yb, Ba, Cd, La, Ce, U, δ¹⁸O‰, and δ¹³C‰ (ed. by V. Anevlavi; ÖAI/ÖAW).

	Sample	Distance	Abs. Prob.	Rel. Prob.	Provenance	Rel. Prob.	Provenance
		1. choice				2. choice
9744	FWM0386	8.2	4.1	100.0	Asenovgrad	0.0	Prokonnesos
9745	FWM0387	1.0	79.0	100.0	Asenovgrad	0.0	Prokonnesos
9752	FWM0394	3.1	36.8	99.4	Asenovgrad	0.6	SE Rhodope
9724	FWM0366	0.9	82.5	100.0	Asenovgrad	0.0	Prokonnesos
9725	FWM0367	10.0	1.8	97.8	Asenovgrad	2.2	Prokonnesos
9726	FWM0368	1.3	71.5	100.0	Asenovgrad	0.0	Prokonnesos
9727	FWM0369	2.9	49.6	99.9	Asenovgrad	0.1	Prokonnesos
9728	FWM0370	5.5	13.7	99.0	Asenovgrad	1.0	Prokonnesos
9729	FWM0371	3.9	27.2	100.0	Asenovgrad	0.0	Prokonnesos
9730	FWM0372	1.5	68.2	100.0	Asenovgrad	0.0	Prokonnesos
9731	FWM0373	3.6	29.7	98.5	Asenovgrad	1.5	Prokonnesos
9732	FWM0374	1.6	65.7	99.9	Asenovgrad	0.1	Prokonnesos
9733	FWM0375	5.3	14.8	99.8	Prokonnesos	0.2	SE Rhodope
9734	FWM0376	0.4	93.1	100.0	Prokonnesos	0.0	SE Rhodope
9735	FWM0377	2.5	46.2	100.0	Prokonnesos	0.0	SE Rhodope
9787	FWM0432	1.0	78.5	100.0	Prokonnesos	0.0	SE Rhodope
9788	FWM0433	1.3	12.1	100.0	Prokonnesos	0.0	SE Rhodope
9750	FWM0392	3.7	29.1	99.9	Asenovgrad	0.1	Prokonnesos
9753	FWM0395	0.9	82.1	100.0	Prokonnesos	0.0	SE Rhodope
9736	FWM0378	4.6	19.9	100.0	Asenovgrad	0.0	Prokonnesos
9737	FWM0379	1.1	75.4	100.0	Asenovgrad	0.0	Prokonnesos
9738	FWM0380	4.0	25.3	100.0	Asenovgrad	0.0	Prokonnesos
9739	FWM0381	4.6	20.3	100.0	Asenovgrad	0.0	Prokonnesos
9740	FWM0382	6.6	8.4	77.1	Asenovgrad	22.9	Prokonnesos
9741	FWM0383	0.9	81.0	100.0	Asenovgrad	0.0	Prokonnesos
9742	FWM0384	2.2	51.6	100.0	Asenovgrad	0.0	Prokonnesos
9743	FWM0385	1.5	66.0	100.0	Asenovgrad	0.0	Prokonnesos
9746	FWM0388	6.3	9.5	82.6	Asenovgrad	17.3	Prokonnesos
9747	FWM0389	1.0	78.4	100.0	Asenovgrad	0.0	Prokonnesos
9748	FWM0390	1.6	64.1	100.0	Asenovgrad	0.0	Prokonnesos
9756	FWM0398	7.2	6.4	100.0	Asenovgrad	0.0	Prokonnesos
9789	FWM0434	0.9	82.0	100.0	Asenovgrad	0.0	Prokonnesos
9749	FWM0391	5.0	16.8	99.5	Asenovgrad	0.5	Prokonnesos
9751	FWM0393	2.4	47.7	100.0	Asenovgrad	0.0	Prokonnesos
9754	FWM0396	9.9	1.9	77.2	Asenovgrad	20.0	SE Rhodope
9755	FWM0397	1.2	74.1	100.0	Asenovgrad	0.0	Prokonnesos
9722	FWM0364	2.7	84.4	99.4	Asenovgrad	0.3	SE Rhodope

).

The selection of variables for multivariate analysis (Mg, Fe, Mn, Sr, Cr, V, Y, Yb, Ba, Cd, La, Ce, U, δ¹⁸O, and δ¹³C) was based on their proven diagnostic value for distinguishing between different marble sources. Trace elements such as Mg, Fe, and Mn are sensitive indicators of the original metamorphic conditions and impurity contents of carbonate rocks and can vary systematically between quarries. Elements such as Sr and rare earth elements (REEs, e.g., Y, Yb, La, and Ce) are particularly useful in provenance studies due to their relative geochemical stability and limited mobility during diagenesis or alteration [32,35,36]. Stable isotope ratios (δ¹⁸O, δ¹³C) complement trace element data by providing additional information on the formation environment of the marble [37,38,39,40]. The combination of these parameters enhances the discriminative power of the multivariate diagrams, enabling a more robust assignment of provenance even when single variables may overlap between sources.

An explanation of the table is provided below:

• Distance: Distance of the sample under consideration from the centre of the ellipse. This centre is the average value of the quarry probability field.
• Relative (posterior) probability: This probability is the degree of likelihood of a sample belonging to a given group (within the selected number of groups). Results below 60% indicate that the sample probably cannot be assigned with certainty and that a second choice has to be considered.
• Absolute (typical) probability: This is the measure of the probability that a sample belongs to a given population. Samples in the centre of the probability ellipse have a high absolute probability. The threshold is 10%, corresponding to samples on the edge of the 90% probability ellipse. Low values indicate anomalous samples (outliers) or samples possibly not belonging to any group in the selection.

5. Discussion

The plethora of marble artefacts unearthed from Philippopolis not only reveals a distinct material preference for diverse object types but also underscores the significance of material qualities and networks in shaping the archaeological landscape. The chronological time span of these materials not only delineates the local quarry exploitation practices but also provides insights into the specific time periods during which imported materials played a pivotal role in the region’s cultural and economic dynamics. Diverse material choices can be observed for the different types of objects, with the architectural complexes being mostly constructed with local stones, with some exceptions of decorated architectural pieces of imported marble.

5.1. The Building Materials

The case of the monumental complex of the Eastern gate and, in particular, the colonnaded street, appears to be a representative example of the combined usage of local and imported material. Figure 5 graphically illustrates the provenance of the sampled architectural elements. The diagram highlights that the majority of structural components—such as pedestals, column shafts, frieze-architraves, cornices, stylobate blocks, and various blocks used in the construction—originate from the local Asenovgrad marble. In contrast, a distinct group of six Corinthian capitals, which served primarily decorative purposes, are made of imported Prokonnesian marble. This selective use of imported material suggests that aesthetic and symbolic considerations were likely prioritised for specific architectural features, such as the Corinthian capitals, while structural and less visually prominent elements were predominantly crafted from local stone. The graphic thus visually reinforces the combined use of local and imported marbles within the architectural programme of the Eastern Gate, reflecting deliberate material choices linked to both functional and representational factors.

According to previous studies, the construction of the complex represents a continuous architectural program, with various structures being added gradually until Late Antiquity [13]. This can be seen through the stylistic observations on the Corinthian capitals, which show the development of patterns and motifs from the early second to the early third centuries AD. Although all Corinthian column capitals follow essentially the same model, the FWM0373 (Asenovgrad) is of better quality and an earlier date than the others. Additionally, even though this capital was not carved at the same time as the others, it is possible that it was later reused alongside them in the colonnades on both sides of the Late antique street leading to the Eastern Gate. Of the group of Corinthian column capitals dating back to the Severan period, six were made of Prokonnesian marble, and only one was made of local Asenovgrad marble, which was also used for the remaining order elements. It is possible that different workshops were responsible for the different pieces; however, the likelihood of finished products (Corinthian capitals) being imported to Philippopolis cannot be excluded. Finally, due to the limited number of capitals made of Prokonnesian marble, it can be hypothesised that these elements were ordered and used as Supplementary Materials near the Asenovgrad material. The combination of coloured stones with white marble for the column order is a well-established phenomenon of second-century Roman Imperial architecture [41] (p. 554). The deliberate use of different white marbles, however, remains an open question in current scholarship. Given that this study presents the first definitive identification of Prokonnesian marble at Philippopolis, it is not yet possible to determine whether the choice was driven primarily by aesthetic considerations, financial factors, or personal preference. The final design of the order may also have depended on the availability of building materials at the construction site [42] (p. 183, n. 72). The dominance of local Rhodope marble highlights the self-sufficiency of Philippopolis and its surrounding region in sourcing structural and decorative materials, reinforcing the significance of local quarrying and workshop traditions. This finding points to a pragmatic approach in material selection, favouring nearby resources for the majority of construction needs [43,44]. However, the targeted import of Prokonnesian marble for select architectural elements signals an engagement with broader imperial networks and stylistic trends, reflecting the city’s position within both regional and supra-regional spheres of influence [45]. Further investigation on the history and typology of the architecture of the Eastern gate is currently being conducted.

5.2. Chronological Remarks

In the case of the Eastern Gate, the first major construction phase occurred in the early second century AD, with many architectural elements dating to this period and being made of Asenovgrad marble (Figure 6). The honorary arch from the time of Hadrian, which was later incorporated into the city gate, was located on the route of the main road Via Diagonalis. The construction of honorary arches to commemorate a particular event or in honour of the emperor was a widespread practice throughout the Roman Empire in the second century AD, and the arch at Philippopolis may indeed have been built for a visit of Emperor Hadrian to the city. As observed in other parts of the empire, the project was likely carried out under imperial patronage [2].

Toward the end of the second century and the beginning of the third century AD, Prokonnesian Corinthian column capitals were introduced alongside one Corinthian column capital made of Asenovgrad marble (Figure 7). These two groups of capitals are contemporary and display a consistent carving style, while an earlier Asenovgrad capital exhibits distinct carving techniques. Thus, the colonnades along the Late antique street were built entirely with earlier architectural elements. As shown in Figure 7, the use of Prokonnesian marble is confined exclusively to the end of the second century AD. Notably, all Prokonnesian artefacts identified in the Eastern Gate complex are Corinthian capitals, and no other architectural components—such as shafts, pedestals, or cornices—were made of this material. This pattern of use suggests a highly selective and intentional choice, likely related to aesthetic or symbolic criteria. The concentration of Prokonnesian marble within this narrow chronological window implies a single or limited phase of importation. This contrasts with the broader use of local Asenovgrad marble across a wider range of architectural types and construction phases, highlighting differentiated procurement strategies for structural versus ornamental components.

5.3. Architectural Remarks

It is still unknown how many structures with architectural decoration were built in and around the Eastern Gate complex. For example, there is no information about the monuments to which the figural relief (FWM0434) and the frieze-architrave with the gladiatorial battle (FWM0559) originally belonged. There are also cases where the same architectural elements were included in the graphic reconstructions of different monuments [5,6,14]. The pilasters (FWM0367) and the only discovered Corinthian pilaster capital (FWM0392) certainly belonged to the construction of the honorary arch (FWM0366). The corner pilasters are decorated on two sides with vertical panels of acanthus scrolls set within a profiled frame. In Asia Minor during the Late Trajanic and Hadrianic periods, scroll patterns became richer and more skillfully executed, spreading rapidly [46]. The Corinthian pilaster capital is adorned with acanthus leaves of Asiatic type and with helices of Attic type. The decorative motifs and workmanship of these architectural details, along with their parallels, suggest a date in the Hadrianic period. It is possible that some of the archivolts (FWM0397) formed vaulted blind niches in the pillars of the honorary arch. Considering the number and variety of entablature parts (FWM0364, FWM0390, and FWM0391), as well as elements not included in this article—e.g., an Ionic cornice—it is possible that there was more than one monument in the area of the complex, built in the first half of the second century AD.

On both sides of the street, dating back to the fourth century AD, massive stylobates have been built (FWM0369–FWM0372), carrying marble colonnades in the Corinthian order, the architectural elements of which were found on the pavement [14]. The reconstruction of the facade of the monumental porticoes includes pedestals with Attic-Ionic bases (FWM0386, FWM0387, and FWM0394); monolithic shafts of free-standing columns with a smooth, polished surface (FWM0378–FWM0381); Corinthian column capitals (FWM0374–FWM0377, FWM0395, FWM0432, and FWM0433); frieze-architraves with a convex frieze (FWM0388, FWM0389, and FWM0398); and a cornice with consoles (FWM0382–FWM0385). All Corinthian capitals discovered in the complex exhibit the characteristic features of provincial Asiatic capitals, and although they are all of similar size, one of them stands out (FWM0373). This capital has different proportions, higher relief, and a better quality of workmanship of the decorative motifs, which is why it can be dated earlier than the other capitals. The larger group of Corinthian column capitals, which have a very similar design, can be dated to the end of the second to the first decades of the third century AD or within the Severan period. The lack of standard helices and the more stylised appearance of the decorative motifs are characteristic of these details. The frieze-architrave, featuring a convex frieze, and the cornice with consoles date from the same period as the capitals. The same generally applies to the decorated archivolt blocks (FWM0396), one of which appears unfinished and reused in the northern stylobate (FWM0372). It is possible that they were included in a more intricate part of the colonnaded street. As is clear, the dating of the order decoration differs from the dating of the street, which leads to the conclusion that the architectural elements in question were reused in the construction of the Late antique porticoes. In search of the original context of the details, the researchers consider the possibility that earlier buildings or an earlier colonnaded street existed [6,14], which is supported by the precise combination of order elements of appropriate size and with similar dating. Only the dating of the column shafts and some of the pedestals with bases is more difficult to determine due to the presence of earlier architectural elements with which they could also be associated.

5.4. Archaeometric Results of Other Building Complexes of Philippopolis

Provenance results for the marble architectural elements of Philippopolis’ Agora, Theatre, and Stadium highlight a dominant use of local Asenovgrad marble, with selective instances of imported Prokonnesian material. In the Agora, both isotopic and multivariate analyses indicate marble primarily sourced from Asenovgrad and Prokonnesos, paralleling the known use of imported decorative pieces in other monumental complexes such as the Eastern Gate. For the Theatre, Asenovgrad marble again predominates. One object was identified as Berkovitsa marble; however, its association with the theatre architecture remains uncertain. Breccia from the nearby Mostovo quarry represents a second material employed alternately within the theatre’s architecture. In the Stadium, analysis again supports the consistent use of Asenovgrad marble. Overall, the results reaffirm the predominance of local marble sources for primary construction, complemented by strategic imports of prestigious Prokonnesian marble for select decorative features, reflecting sophisticated material choices within Roman Philippopolis’ urban fabric. The publication of the above results is now in progress.

Building upon the results of the present study, future research will expand the scope of marble provenance investigations to additional urban centres across Roman Thrace and the wider Balkan region. Ongoing work is currently focusing on architectural elements from Augusta Traiana, which will further contribute to the understanding of local quarry exploitation and material selection in regional architectural programmes. In the longer term, it would be particularly valuable to investigate whether local marbles, such as those from the Asenovgrad or Mostovo quarries, were exported and incorporated into monumental architecture in neighbouring provinces. A systematic comparative study of architectural materials across key cities in the Balkans would provide important insights into the dynamics of stone trade, workshop practices, and the extent of regional economic and cultural connectivity during the Roman Imperial period. This represents a promising direction for future research.

5.5. Remarks on the Wider Context of Roman Stone Trade

Each Roman province developed its own micro-network of stone trade, shaped by the availability of local resources and its integration into wider regional and supra-regional markets. Comparative studies across the empire reveal that patterns of stone preference, workshop distribution, and trade routes varied locally but were also interconnected, reflecting broader dynamics of the imperial economy. Analysing similarities and differences between provinces thus contributes to a more comprehensive understanding of stone trade and market function in the Roman world.

In the Iberian Peninsula (present-day Spain and Portugal), extensive studies have examined the exploitation of local quarries and the circulation of decorative stones. From ca. 200 BC to 300 AD, the exploitation of stones, minerals, and metals generated considerable wealth, facilitated by the regional road network, notably the Via Herculea/Via Augusta [47]. Alongside abundant local stone production, imported marbles—particularly coloured varieties such as Africano, Cipollino mandolato, and Porfido rosso antico—are documented in at least seventeen archaeological sites [48], illustrating the integration of Iberian cities into the empire-wide trade of luxury stones [49].

A comparable pattern is observed in the provinces of Noricum and Pannonia (present-day Austria, Slovenia, and parts of Hungary), where rich local marble sources and active metal mining fostered a strong regional stone economy [50]. The administrative boundaries of Noricum, Pannonia Superior and Inferior, and Moesia Superior did not hinder stone circulation; instead, evidence shows that marble products were widely exchanged across these provinces [51], underscoring the permeability of provincial borders within the imperial trade system.

The case of Philippopolis fits within this broader picture. The combination of locally sourced marble from the Rhodope region and imported Prokonnesian material observed at the Eastern Gate reflects a similar pattern of selective importation embedded within a predominantly local supply system. Such parallels highlight how provincial centres adapted their material choices to balance local resources, aesthetic preferences, and participation in wider imperial trade networks.

6. Conclusions

The archaeometric investigation into the provenance of marble architectural elements from Roman Philippopolis has yielded significant insights into the city’s urban and economic development during Antiquity. The interdisciplinary methodology, employing petrographic analyses, stable isotope ratios, and trace element profiles, has effectively differentiated local marble sources from imported materials. The majority of the studied artefacts, predominantly structural and decorative architectural elements, were conclusively identified as originating from the local Rhodope quarries near Asenovgrad, emphasising a deliberate and consistent use of regional resources throughout the city’s major construction phases.

Notably, certain decorative Corinthian capitals were traced to distant Prokonnesian quarries, highlighting the selectivity of material importation, possibly due to aesthetic preferences or symbolic prestige. This selective use underscores the complexity and sophistication of marble trade networks and points towards well-established economic and cultural connections with regional and supra-regional quarry sites during the Roman Imperial period.

Chronologically, the research has clarified aspects of construction phases and the reuse of architectural elements, particularly during Late Antiquity. The identification of multiple marble sources within the Eastern Gate complex illustrates evolving practices in material selection and architectural decoration across different historical periods, reflecting both continuity and innovation.

The nuanced application of archaeometric methods has not only provided clarity on the geological origins of the marble used but also offers a broader understanding of socio-economic factors, such as regional trade dynamics, workshop practices, and architectural patronage. Future research, integrating additional archaeological and historical data, could further unravel the mechanisms behind marble selection and procurement strategies, as well as their implications for the cultural landscape of Roman Philippopolis.

Finally, the application of marble provenance studies provides critical support for informed conservation strategies. By scientifically determining the origin of construction materials, these methods enable the careful selection of repair stones that are structurally and visually compatible with the original fabric. This reduces the risk of introducing unsuitable materials that could accelerate deterioration or undermine the historical integrity of the monument. Furthermore, integrating petrographic, isotopic, and geochemical analyses into conservation planning enhances transparency and accountability in restoration decisions. Rather than relying solely on stylistic or visual assessments, provenance data anchors interventions within a robust analytical framework [52,53]. This approach reinforces the authenticity, reversibility, and sustainability of conservation efforts, ensuring that restoration interventions respect the material history and architectural significance of the ensemble.