Aquae Sulphurae Archaeological Park: A Roman Thermal Spa Complex near Sarajevo
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Country: Bosnia and Herzegovina
Civilization: Byzantine, Roman
Remains: City
Context
The Aquae Sulphurae Archaeological Park is located near Ilidža, a suburb southwest of Sarajevo in Bosnia and Herzegovina. Positioned within the Sarajevo basin, the site occupies a valley distinguished by natural sulphur-rich thermal springs and a karstic landscape. These geothermal waters have historically shaped the settlement’s development, providing a natural resource that attracted human habitation and therapeutic use from antiquity onward. The surrounding terrain combines river valleys, notably the Željeznica River, with nearby mountainous areas, creating a diverse ecological setting conducive to settlement and resource exploitation.
Archaeological investigations have established that Aquae Sulphurae was primarily occupied during the Roman period, when it functioned as a specialized spa complex. The thermal springs were utilized from at least the 1st century CE, with continuous activity into late antiquity. Although the site experienced decline by the 4th or 5th century CE, the precise reasons remain unclear due to limited direct evidence. The park today preserves structural remains and artifacts that illuminate its role within the network of Roman provincial settlements in the central Balkans. Ongoing conservation and research efforts aim to safeguard its thermal and architectural heritage while enhancing scholarly understanding of its historical context.
History
The Aquae Sulphurae Archaeological Park near Ilidža embodies a layered historical narrative spanning from indigenous Illyrian occupation through Roman urbanization and into the early medieval period. Initially inhabited by the Desitiati, an Illyrian tribe noted for metalworking and fortified hilltop settlements, the area’s natural resources, including thermal springs, supported sustained indigenous communities. With Roman conquest, the site developed into a vicus centered on its sulphur springs, eventually attaining municipium and colonia status, reflecting its administrative and therapeutic significance within the Roman province. The settlement’s decline in late antiquity corresponds with regional political and social transformations, though it maintained some local relevance into the early medieval era.
Pre-Roman and Indigenous Period (Before 1st century CE)
Prior to Roman annexation, the Sarajevo plain was occupied by the Desitiati, an Illyrian tribe recognized for their advanced metalworking skills and complex social organization. Their settlements were typically located on elevated terrain, including hillforts (castella) and oppida, which served as territorial centers. Notable nearby sites include Gradac (Ilinjača) and Gradina in Zenika, situated close to present-day Ilidža. Although no direct archaeological remains from this period have been identified within the Aquae Sulphurae site itself, the proximity of these indigenous centers and the presence of thermal springs suggest the area’s early importance for settlement and ritual use. The region’s rivers and mountainous resources supported a stable indigenous population prior to Roman integration.
Roman Conquest and Early Roman Period (1st century CE)
Following the Roman conquest of Illyrian territories in the 1st century BCE, the settlement of Aquae Sulphurae was established on the left bank of the Željeznica River, strategically positioned near natural sulphur-rich thermal springs. By the late 1st century CE, epigraphic evidence confirms the existence of a vicus with spa facilities, as indicated by inscriptions referencing the “Aquae S… Baths.” The settlement’s location along a major Roman road connecting Narona (modern-day Vid) through the Neretva valley to the Sarajevo basin enhanced its accessibility and economic integration. This period marks the initial phase of Roman urban influence, with the site serving as a local center for healing and recreation within the imperial infrastructure.
Imperial Roman Period (2nd–4th centuries CE)
During the 2nd century CE, under Emperor Marcus Aurelius (161–180 CE), Aquae Sulphurae was elevated to the status of a Roman colony, likely through the settlement of military veterans who received land grants (ager) in the Sarajevo plain. The Constitutio Antoniniana of 212 CE extended Roman citizenship to provincial inhabitants, further consolidating the colony’s municipal institutions. The colony’s territory encompassed a broad area of the Sarajevo basin, including rural settlements and villa estates extending north to Breza and Podlugovi, northwest to Kiseljak and Busovača, and south to Pazarić and Tarčin, establishing Aquae Sulphurae as the administrative and political center of the region.
Throughout the 2nd and 3rd centuries CE, the settlement expanded its urban fabric, developing specialized thermal spa complexes and residential architecture. Excavations have revealed a villa urbana adorned with elaborate mosaics and frescoes, alongside a large hospitalium complex featuring hypocaust heating and sophisticated water management systems. These structures attest to the site’s function as a healing and recreational center. The settlement’s municipal status advanced during the 3rd century, culminating in its recognition as a res publica under Emperor Diocletian (284–305 CE), reflecting increased local autonomy and political prominence within the Roman Balkans.
Late Antiquity (4th–6th centuries CE)
The 4th and 5th centuries CE saw a gradual decline in Aquae Sulphurae’s urban vitality, consistent with broader regional instability during the late Roman Empire. Archaeological evidence indicates reduced construction activity and maintenance of public buildings, although the site remained inhabited into the 6th century. The decline in spa use and administrative functions likely resulted from a combination of political upheavals, economic contraction, and shifting settlement patterns in the Balkans. While no direct evidence links the decline to specific military events or natural disasters, the period was marked by frequent incursions and administrative reorganization. Despite diminished status, Aquae Sulphurae retained some local significance during this transitional era.
Early Medieval Period (7th–12th centuries CE)
Following the collapse of Roman authority in the region, Aquae Sulphurae experienced limited but continuous occupation during the early medieval period. Material culture, including pottery and jewelry dated from the 9th to 12th centuries, attests to ongoing habitation or reuse of the site. Seventeen displaced late medieval stečak tombstones found on the site further indicate its cultural relevance during this time. However, no substantial architectural remains from the early medieval period have been identified, and the site’s precise role remains poorly documented. The population was likely smaller and ethnically mixed, reflecting the broader demographic shifts in the post-Roman Balkans.
Modern Rediscovery and Archaeological Research (19th century–Present)
The archaeological significance of Aquae Sulphurae was first recognized in 1876 by Arthur Evans, with systematic excavations initiated during Austro-Hungarian rule in the 1880s. Early investigations by scholars such as Carl Patsch and Čiro Truhelka uncovered mosaics, villa remains, inscriptions, and artifacts, many of which are now housed in the National Museum of Bosnia and Herzegovina in Sarajevo. Excavations continued intermittently throughout the 20th century, revealing the extent of the Roman thermal complex and associated structures. Conservation efforts, particularly in the late 20th century, have focused on preserving architectural remains and mosaics. The site was declared a National Monument of Bosnia and Herzegovina in 1967 and remains a subject of ongoing archaeological research aimed at refining its chronology and regional significance.
Daily Life and Importance by Period
Roman Conquest and Early Roman Period (1st century CE)
During its initial Roman phase, Aquae Sulphurae functioned as a vicus centered on the exploitation of its sulphur-rich thermal springs. The population comprised a mixture of Roman settlers, including veterans, indigenous Illyrians, artisans, and spa attendants. Social organization likely reflected Roman municipal norms, with households consisting of nuclear families supported by slaves or freedmen. Economic activities focused on spa-related services such as bath attendants and healers, alongside small-scale artisanal production of pottery and metal goods. The settlement’s position on a major Roman road facilitated trade and the supply of agricultural products from surrounding estates. Dietary evidence, including amphora fragments, suggests consumption of bread, olives, local fish, and imported wine and olive oil. Clothing styles conformed to Roman provincial fashions, with tunics and cloaks common to both sexes. Religious life incorporated Roman deities, notably Apollo Tadenus, associated with healing, as attested by inscriptions. Local magistrates administered civic affairs, integrating the settlement into imperial structures.
Imperial Roman Period (2nd–4th centuries CE)
With its elevation to colonia status, Aquae Sulphurae experienced urban expansion and increased social stratification. The population included Roman veterans granted land, affluent landowners, skilled artisans, and a service class supporting the spa complex. Epigraphic evidence documents civic officials such as duumviri, indicating structured municipal governance. Elite households employed slaves and freedmen, while women participated in domestic management and religious cults. The economy diversified to include large-scale agriculture on villae rusticae producing grain, olives, and wine, as well as artisanal pottery workshops marked by stamped amphorae (e.g., “COSSII”). The hospitalium accommodated visitors, reflecting a developed health tourism sector. Advanced water management and hypocaust heating systems supported these functions. Dietary remains indicate a Mediterranean diet rich in fish, olives, and cereals. Villas featured richly decorated interiors with mosaics depicting marine motifs and frescoes in vibrant colors, demonstrating cultural refinement. Trade flourished along the road connecting Narona to the Sarajevo basin, facilitating import and export of goods. Religious practices combined Roman imperial cults with local traditions, including dedications to Apollo Tadenus and imperial honors to Diocletian. Public festivals likely accompanied spa activities, reinforcing social cohesion. Aquae Sulphurae served as the administrative center of a broad ager, with local councils managing civic and religious affairs, underscoring its regional importance.
Late Antiquity (4th–6th centuries CE)
During late antiquity, Aquae Sulphurae underwent demographic contraction and diminished urban vitality. The population decreased, with fewer elite families maintaining estates and a decline in public officials’ prominence. Household structures simplified, and some villas fell into disrepair, though limited occupation persisted. Economic activity contracted, focusing on local subsistence rather than extensive production or trade. Spa facilities saw reduced maintenance, and workshops declined. Food consumption became more localized, relying on staple crops and limited animal husbandry. Architectural upkeep and interior decoration deteriorated, with mosaics and frescoes showing neglect. Clothing styles simplified, reflecting reduced economic means. Transport and trade diminished, with fewer goods moving along regional routes. Religious life shifted as Christianity spread, though direct evidence at the site is limited. Pagan cults, including that of Apollo, likely declined, replaced by emerging Christian communities. Civic structures weakened amid political instability and external pressures. Despite decline, the site retained modest local significance as a spa and administrative locale into the 6th century.
Remains
Architectural Features
The archaeological remains at Aquae Sulphurae predominantly date from the 1st to 4th centuries CE, illustrating its development as a Roman thermal spa settlement. The site is situated on the left bank of the Željeznica River, where natural sulphur springs dictated the settlement’s spatial organization. Construction employed local limestone and sandstone, utilizing masonry techniques such as opus incertum (irregular stonework) and opus quadratum (regular squared blocks). Roofs were covered with Roman ceramic tiles (tegulae and imbrices). Foundations were often excavated to depths of up to one meter to address damp ground conditions. The urban fabric includes residential villas, public buildings, and spa-related structures arranged around courtyards and aligned roughly along a north-south axis. The remains reveal a complex settlement with specialized functions, including healing baths, guest accommodations, and elite residences. Over time, the site expanded from a modest vicus to a municipium and later a colonia, with architectural enhancements such as porticoes and mosaic decoration added during the 2nd and 3rd centuries CE.
Presently, visible remains include foundations, wall fragments, mosaic floors, and stone architectural elements. Some structures are partially overgrown or buried due to modern development. The site’s layout centers on the thermal springs, with archaeological evidence of integrated water management and hypocaust heating systems within the spa complex. Preservation varies, with some buildings extensively excavated and conserved, while others remain fragmentary or incompletely studied.
Key Buildings and Structures
Complex of Villas around Hotel Bosna
Underneath the modern Hotel Bosna in Ilidža lies a complex of five Roman villas primarily dating to the 1st century CE. Excavations uncovered the foundations of a large residential building beneath the hotel’s north-eastern entrance, featuring a well-preserved mosaic depicting the head of a woman interpreted as the nymph of the thermal springs. This central medallion is surrounded by marine motifs including fish and seahorses, exemplifying high-quality Roman mosaic art with rich coloration and detailed craftsmanship. Further excavations to the north and east revealed that this building was part of a larger residential complex. Nearby, a rectangular structure measuring approximately 19.22 by 12.33 meters was excavated, containing mosaics with geometric designs dated to the late 1st or early 2nd century CE.
Villa Urbana (Building A)
The villa urbana, located about 75 meters west of the Hotel Bosna complex, is fully excavated and dates from the 1st century CE with additions in the 2nd or 3rd century. It has a roughly square plan measuring 33.9 by 36.85 meters, comprising approximately thirty rooms arranged around a central peristyle courtyard. The east side features a portico added in the later period, facing a side road or local market square. Walls were constructed from local limestone and sandstone using quarry stone and mortar, with facings of slab-like stone, opus incertum, and opus quadratum. The roof was tiled with tegulae and imbrices. Floors were primarily river aggregate and screed, with three rooms containing mosaic pavements.
Room 21 (10 by 8 meters), likely serving as a triclinium or tablinum, contains a finely preserved mosaic featuring heart-shaped designs, rhombs, medallions with sea symbols, birds, and a tree of life flanked by antelopes. Room 13’s mosaic, covering 39 square meters and discovered in 1955, includes geometric and figural motifs such as probable personifications of the seasons, quadrifoil rosettes, and a double meander border. Room 22 contains a mosaic fragment with geometric patterns including a Greek key meander and linked rhombs. Walls bear fresco fragments with straight and wavy lines in red, green, ochre, and grey. Stone mouldings include a pedestal and column base with plinth in the peristyle area.
Archaeological finds within the villa include an amphora neck stamped “COSSII,” provincial terra sigillata shards, terra nigra, coarse local pottery, terracotta lamps, and conical wedges for amphorae. Twenty-five Roman coins dating from 42 CE to 364–375 CE were recovered, alongside a bronze belt buckle, glass shards, a bone needle, fibulae, cosmetic wares, an arrowhead, and nails.
Unidentified Building (Building B)
Located between the villa urbana and the hospitium, approximately 30 meters from the villa, this building’s layout and function remain uncertain due to incomplete excavation. Its walls align with those of the adjacent buildings. The structure has suffered partial destruction from gravel road construction to the north and is buried under soil to the south. Three coins found here date from 98–118 CE and 364–378 CE, indicating occupation or use during these periods.
Hospitium / Hospitalium (Building C)
This public building lies northeast of the villa urbana and covers approximately 2,880 square meters. Constructed in the 2nd or 3rd century CE, it originally functioned as a thermal complex with a healing spa (pars balnearia) and recreational facilities. Later expansions added guest rooms (hospitium). The building comprises multiple rooms arranged around an inner courtyard. Walls and foundations were built using slab-like and rough-cut stone with a quarry stone and mortar core. Outer walls measure between 70 and 76 centimeters thick, while interior walls range from 56 to 60 centimeters. The roof was covered with tegulae and imbrices tiles.
Flooring includes terracotta tiles, hexagonal cuneiform cubes, screed, and mosaics. Seven rooms had mosaic floors, with three relatively well preserved and four fragmentary. Mosaic bases were made of lime mixed with ground brick, with tesserae mostly white and grey. Designs include geometric bands, rectangles, squares, and two dolphin figures. These mosaics date stylistically to the 3rd and 4th centuries CE, reflecting changes in artistic style during social crises. Minor fresco fragments survive. Stone mouldings found include part of an architrave slab, three bases, several capitals, and two fragments of fluted columns. Fifteen coins dating from 253–268 CE to 276–282 CE were recovered, along with a small thin-walled vessel without ornamentation.
Thermal Springs and Spa Facilities
The settlement developed around natural sulphur thermal springs on the left bank of the Željeznica River. The thermal complex, constructed mainly in the 2nd and 3rd centuries CE, formed the core of the settlement. Spa facilities included healing baths and recreational areas equipped with advanced water management and hypocaust heating systems, as evidenced in the hospitium and related structures. The thermal springs remain a defining element of the site’s layout and function.
Archaeological Discoveries
Excavations at Aquae Sulphurae have yielded a diverse assemblage of artifacts spanning from the 1st to 4th centuries CE, with some evidence of later use into the early medieval period. Pottery finds include provincial terra sigillata, terra nigra, coarse local wares, and amphorae, some stamped with “COSSII,” indicating local ceramic and brick production workshops. Terracotta lamps and conical wedges for amphorae were also recovered.
Epigraphic finds include an altar dedicated to Apollo Tadenus by Harmidis, a slave of the colony, and an inscription honoring Emperor Diocletian on a Roman bridge at Ilidža. These confirm the settlement’s status as a municipium, colony, and later res publica during the 3rd century CE. Additional inscriptions comprise epitaphs, dedications to deities, and imperial honors.
Coins totaling 63 pieces were discovered, dating from 42 CE to 375 CE, representing a broad chronological range of occupation. Other finds include bronze and iron tools, jewelry such as fibulae, cosmetic items, arrowheads, glass fragments, and bone needles. These artifacts were recovered from domestic quarters, workshops, and public buildings, reflecting diverse aspects of daily life and economic activity.
Mosaic art is well represented, with at least twelve mosaics uncovered in the villa urbana complex. Motifs include geometric patterns, octagonal stars, sferic rhombs, dolphins, fish, theatrical masks, rosettes, Gordian knots, and figural representations such as nymphs and Amor riding a sea horse. The mosaics date mainly from the 1st to 4th centuries CE. Some mosaics remain in situ, while others are housed in the National Museum of Bosnia and Herzegovina in Sarajevo. A local mosaic workshop active in the 2nd century CE produced these artworks.
Preservation and Current Status
The preservation of Aquae Sulphurae’s remains varies across the site. Foundations and mosaic floors of the villa urbana and hospitium survive but are partially overgrown with dense vegetation. Conservation and restoration efforts during the late 20th century have stabilized and preserved mosaics and structural walls, particularly in the villa urbana and hospitium. Building B remains partially destroyed and buried due to modern road construction. Stone architectural fragments, including mouldings and column elements, are scattered throughout the site. Seventeen displaced late medieval stečak tombstones found on the site indicate later cultural activity. Geophysical surveys have identified additional Roman structures, such as colonnaded walkways and ramparts, though these remain unexcavated. Modern development and vegetation growth pose ongoing challenges to preservation. Movable artifacts are curated in the National Museum in Sarajevo, ensuring their protection and study.
