Pliska, the first capital of the medieval Bulgarian state, covered a territory so vast that modern researchers are still mapping its full extent. Stretching across nearly nine square miles of what is now northeastern Bulgaria, the site contained stone citadels, a network of underground passages, and a large oval enclosure that archaeologists have struggled to explain for decades. Successive waves of investigation, from early 20th-century excavations to recent non-invasive geophysical surveys, have gradually revealed a planned urban center whose scale challenges long-held assumptions about early medieval state power in southeastern Europe.
Eight decades of fieldwork at a sprawling capital
Scholarly attention to Pliska dates back at least to 1939, when an article on the site appeared in the journal Antiquity, one of the field’s most respected publications. That early report documented massive ramparts and interior structures whose dimensions surprised researchers who had expected a compact fortress rather than a sprawling administrative center. The 1939 account established Pliska as a subject of serious international archaeological interest and set the baseline against which later findings would be measured.
Decades of traditional excavation followed, gradually exposing stone walls, water channels, and residential quarters spread across the site’s enormous footprint. Teams opened trenches in and around the inner stone fortress, traced sections of the defensive earthworks, and documented building foundations that hinted at workshops, storage facilities, and elite residences. Yet conventional digging could cover only small fractions of the total area at a time, leaving large zones between the inner citadel and the outer earthen ramparts essentially unexamined. That gap in coverage meant that the full layout of the capital, and the relationship between its monumental core and its outer districts, stayed poorly understood well into the 21st century.
Archival notes from mid-century campaigns show how often archaeologists had to choose between depth and breadth: either concentrate on a known monumental complex or attempt wide but shallow sampling across the plain. In practice, limited budgets and short field seasons favored targeted work, reinforcing an image of Pliska dominated by its stone palace and fortifications. The surrounding landscape, though clearly enclosed and structured, remained a kind of archaeological blank space on published maps.
Geophysical surveys redraw the map
A turning point came with the publication of an integrated geophysical prospection study in the Bulgarian e-Journal of Archaeology (BE-JA), volume 9, pages 229 through 261. This research, accessible through the BE-JA digital edition, combined magnetometry and electrical resistivity data to scan broad sections of the site without breaking ground. By layering these non-invasive techniques, the research team produced subsurface maps that revealed previously unknown structural features buried beneath agricultural fields surrounding the inner fortress.
The geophysical survey covered both previously excavated areas and large tracts that had never seen a trench. Magnetometry detected variations in the Earth’s magnetic field caused by buried walls, ditches, and burned surfaces, while resistivity measurements tracked how electrical currents moved through different soil types, highlighting stone foundations and filled pits. When these datasets were processed together, subtle patterns emerged: rectilinear building plans, road-like linear anomalies, and clusters of smaller features that may represent workshops or domestic compounds.
The study built directly on the spatial framework first outlined in the 1939 Antiquity report, but it exposed significant gaps in older hand-drawn site plans, particularly in the zones between the stone citadel and the outer defensive perimeter. Areas once thought to be largely empty now showed evidence of dense activity. Regularly spaced anomalies suggested a more formal street grid than earlier excavators had suspected, while larger magnetic signatures pointed to substantial but previously undocumented complexes beyond the inner walls.
Among the most striking discoveries was the detection of a large oval enclosure whose function has not been conclusively determined. Described informally as a “mysterious arena,” the feature appears in the geophysical data as a distinct bounded space with internal anomalies that could indicate seating, partitions, or activity surfaces. The enclosure’s outline cuts across some of the rectilinear patterns seen elsewhere, implying that it may represent a separate planning episode or a specialized zone within the broader urban layout. No excavation trench has yet cut through this enclosure in a way that would settle the question of its purpose, leaving researchers to speculate about whether it served as a gathering place, a livestock corral, a ceremonial ground, or some combination of uses across different periods of the capital’s history.
What is verified so far
The strongest confirmed facts center on Pliska’s status and the documentary trail surrounding it. Pliska is identified as the first Early Medieval Bulgarian capital in both the BE-JA geophysical study and the University of Vienna repository entry that catalogues the same research. The 1939 article in Antiquity established the site’s importance in the English-language scholarly record, and its core observations about rampart scale and interior complexity have not been contradicted by later work. The BE-JA paper’s appearance in a peer-reviewed journal and its parallel listing in a major European university’s research portal together confirm that the geophysical data have passed formal academic review.
The physical evidence for stone citadels and underground passages rests on a combination of the older excavation record and the newer geophysical anomalies. Magnetometry readings show linear high-resistance or high-contrast features consistent with stone wall foundations, while lower-resistance channels suggest subterranean conduits, whether for water management, defensive movement, or storage. These readings align with structures partially exposed during earlier digs, such as vaulted corridors and drainage systems, giving researchers confidence that the geophysical interpretations are reliable even where no trench has been opened.
Similarly, the scale of the outer earthworks is no longer in doubt. The ramparts documented in the 1939 publication have been traced in subsequent surveys and confirmed by the recent prospection work, which shows their continuous course around a vast enclosed area. The combination of massive defensive architecture, internal stone complexes, and an organized network of ancillary buildings supports the view of Pliska as a planned capital rather than a loosely aggregated settlement.
What remains uncertain
Several significant questions stay open. The exact dimensions of the oval enclosure have not been published in the available primary sources, and no soil samples or stratigraphic profiles from within the feature have been reported. Without that physical evidence, the enclosure’s date of construction, its phases of use, and its abandonment sequence all remain speculative. One working hypothesis holds that the space functioned as a multi-phase livestock and assembly area that contracted after the Bulgarian capital relocated to Preslav, but this scenario has yet to be tested against excavated material.
More broadly, the social and administrative functions of the newly mapped districts are still being debated. Geophysical signatures can suggest building density and layout, but they cannot by themselves distinguish elite residences from barracks, or workshops from storage compounds. Only targeted excavation, combined with careful study of artifacts and environmental remains, will clarify who lived and worked in these quarters and how they related to the ruling court inside the stone citadel.
Chronology is another unresolved issue. While the main phases of Pliska’s occupation are broadly known from historical sources and earlier digs, the fine-grained sequence of construction and remodeling across the nine-square-mile landscape remains hazy. Did the outer districts grow steadily from an initial core, or were they laid out in large, planned expansions? Did the oval enclosure precede the surrounding buildings, or was it inserted into an already dense urban fabric? The current data cannot yet provide definitive answers.
A capital city still coming into focus
What the last eight decades of research do show is that Pliska was far more than a fortress with a palace. It was a vast, organized capital whose defenses, infrastructure, and enigmatic open spaces reflected the ambitions and capabilities of an early medieval state operating on a scale once thought unlikely for the region. The integration of traditional excavation with wide-area geophysical prospection has transformed understanding of the site’s layout, revealing hidden districts and puzzling features like the oval enclosure.
Future work will almost certainly refine this picture, as archaeologists use the geophysical maps to guide selective digging, test competing interpretations, and anchor the subsurface patterns in datable, material evidence. For now, Pliska stands as a reminder that even well-known capitals can still surprise, and that beneath the ploughed fields of northeastern Bulgaria, much of this early medieval metropolis remains to be explored.
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*This article was researched with the help of AI, with human editors creating the final content.
