Nessebar, Ancient Mesambria (Mesembria)
is one of the most significant, important, and internationally recognised cultural and historical sites in Bulgaria. In 1983, it was inscribed on the UNESCO World Heritage List due to its authentic appearance, unique landscape, and numerous well-preserved cultural monuments – both on land and underwater.
Underwater investigations in the area of Nessebar began in 1960 at the initiative of two of the founding figures of Bulgarian archaeology – Ivan Venedikov and Velizar Velkov, who led the land-based research. The underwater studies were entrusted to Lyuba Ognenova-Marinova – one of the pioneers of Bulgarian underwater archaeology. These investigations were carried out by the diving team of the Bulgarian Academy of Sciences, and later by the underwater research group of the National Expedition Club “UNESCO.” In total, they conducted 15 underwater archaeological expeditions during the 1960s, 70s, and 80s, the last of which took place in 1984. At the time, an appropriate methodology was applied, aimed at documenting the submerged parts of the Nessebar Peninsula. These long-term studies established that Mesambria had lost about one-third of its fortified area due to rising sea levels, land subsidence, erosion, and abrasion. As a result, remains of fortification walls, towers, staircases, and artefacts from the pre-Roman era, Late Antiquity, the Middle Ages, and the Bulgarian National Revival period were found in various sectors of the peninsula’s waters. These structures were built using various techniques – from large stone blocks or flat stones without mortar, to combinations of stone, mortar, and bricks (opus mixtum). They were discovered both in the surf zone and at depths of 2–3 and 5–6 metres.
Along the entire northern coast of the Nessebar Peninsula, sections of fortification walls were identified following the shoreline at depths of up to 1.5 metres. The northern wall begins north of the town’s western gate and continues underwater to the east at distances of up to 40 metres from the shore. To the east and southeast of the peninsula, sections of walls, towers, and bastions have also been discovered.
Based on a comprehensive analysis of written and epigraphic sources, as well as archaeological data from both land and underwater excavations, several key buildings that slid into the sea have been identified: the ancient theatre and the temple of Zeus and Hera, the Early Christian basilica near the medieval church of St George the Old, the northern nave of the basilica of the Virgin Eleusa, and the medieval churches of St Stephen the Acropolitan and Christ the Acropolitan. So far, there is no firm evidence of extramural urban development.
The intense abrasion and landslide processes at the end of the 1980s and during the 1990s were mitigated through the construction of shoreline fortifications, mainly along the northern and eastern coasts of the peninsula. The underwater archaeological structures revealed in the 1970s and 1980s along the northern coast, after conservation, now lie beneath the pavement of land reclaimed from the sea. This activity did not affect the fortification walls and the scattered underwater artefacts southeast and northwest of the peninsula, which remain accessible for new investigations.
CUA Investigations
In 2015, the CUA resumed archaeological research in Nessebar – initially with rescue investigations, and from 2017 onward with regular excavations, funded annually by the Ministry of Culture and supported several times by the Balkan Heritage Foundation. The CUA team’s research questions include: What is the landscape evolution of the Nessebar Peninsula? How much of the ancient city was destroyed by erosion? What are the preserved underwater structures and how are they dated? Where were the ancient harbours located? What is the condition of the underwater remains, and what are the possibilities for their display and integration into cultural tourism?
Using integrated geophysical surveys and drone-based photogrammetry, a high-resolution digital terrain model was created for the peninsula and its adjacent waters. The three-dimensional bathymetric model provided a geographic basis for mapping the recorded structures and helped interpret the location logic of Nessebar’s fortification systems across different historical periods, the scale of the ancient city, and the extent of its submerged coastal areas. A high-resolution orthophoto mosaic and sonar mosaic were also produced, which, along with the terrain model, guided diving surveys and targeted inspections in zones of high archaeological potential.
To date, the CUA team has rediscovered and documented, using modern methods, structures previously studied by L. Ognenova. New and previously unknown archaeological features were also discovered – stone breakwaters forming parts of the city’s southeastern harbour (the largest ancient architectural structures discovered so far in the Black Sea), fortification wall sections built with different construction techniques from the pre-Roman and Late Antique periods, elements of the ancient street system, architectural fragments, and more.
In 2018, 2020, and 2022, CUA, together with the Balkan Heritage Foundation, organised an International Underwater Archaeology Field School, accredited by New Bulgarian University and Connecticut College (USA).
During the excavations, CUA also organised volunteer campaigns in which divers from the “Friends of the Sea” association and various diving clubs participated in the archaeological work.