Nessebar is one of the Bulgaria’s most significant and world-recognized cultural and historical sites. It was inscribed in the UNESCO List of the World Heritage Sites in 1983 due to its authentic appearance, unique landscape and many preserved historical monuments both on land and underwater.

The earlier documented human occupation of the peninsula of Nessebar refers to the end of the Bronze Age when the area was settled by Thracian tribe. Its name, which was originally Mesambria, originates from the Thracian words “Melsas”, the name of the legendary founder of the settlement and “bria”, the Thracian word for town. It is situated on a small peninsula (currently about 0.5 sq. km) that was connected to the mainland by a narrow isthmus. Mesambria’s first Greek colonizers were of Dorian origin who settled there at the end of the 6th century BCE. The town grew quickly and became one of the most powerful Greek colonies along the western Black Sea coast. It had several temples, a qymnasium, a theatre, massive administrative buildings and corresponding infrastructure. The town, called already Mesembria, was also gradually surrounded by massive fortification walls. According to the ancient sources it had two harbours, one to its north and another to its south.

It reached the peak of its prosperity in the 3rd – 2nd centuries BCE, at which point it even minted its own gold coins. Commercial links connected it to towns from the Black Sea, Aegean and Mediterranean coasts. Numerous imported precious artifacts now displayed in the Archaeological Museum of Nessebar provide material expression of the site’s rich economic, cultural and spiritual life in this period. In 72 BCE, the town was conquered by Roman armies without resistance. In the beginning of the 1st century CE, it was included within the borders of the Roman Empire. After the capital was moved to Constantinople in 324 CE and Christianity was accepted as the official religion of the Empire in 313 CE, favourable conditions arouse for the renaissance of the town. New Christian basilicas, fortification walls, and water supply lines were built in the following centuries.

The city was besieged and taken for the first time by the Bulgarians in 812 CE. It was situated in border region between the Byzantine Empire and the First Bulgarian State (Chaganate) and periodically changed hands between the two powers. During the 12th and 13th centuries, active trade links were developed between Nessebar and some Mediterranean and Adriatic towns, such as Constantinople, Venice, Genoa, Pisa, Ancona, and Dubrovnik (Ragusa) as well as with the countries along the Danube River. During almost its entire Christian history, Nessebar was the seat of a bishop. Many churches and monasteries were built in the city and its surroundings reflecting its prosperity and richness.

Nessebar fell under Ottoman rule together with the Byzantine capital Constantinople in 1453 CE. During the following centuries, the economic and spiritual life did not stop and Nessebar’s harbour continued to be an important import and export center. The shipyard’s production, one of the main subsidence of the town, served the Ottoman fleet and the local merchants. In 1878 Nessebar was liberated from the Ottomans and included into the borders of the Principality of Bulgarian.

Underwater archaeological researches in the waters off Nessebar – 1960-1984

Underwater research in the waters off Nessebar began in 1960 in initiative of the leading Bulgarian archaeologists at the time – Ivan Venedikov and Velizar Velkov, directors of the on land excavations. Underwater research was conducted by Lyuba Ognenova-Marinova, who became the first woman archaeologist and diver in Bulgaria and one of the pioneers of the Bulgarian underwater archaeology.

Underwater surveys were carried out by the diving group of the Bulgarian Academy of Sciences and later by the underwater research group of the National Expedition Club “UNESCO”. Altogether, they run 15 underwater archaeological expeditions in the 1960s, 1970s and 1980s (the last one in 1984) and recorded numerous submerged remains of the ancient town. The long-standing research found out that Mesambria lost about 1/3 of its fortified territory due to sea level rise, land subsidence, landslides, erosion and abrasion. As a result, remnants of fortress walls, towers, staircases and artefacts from the pre-Roman era, Late Antiquity, Middle Ages and the Revival period were discovered in various sectors of the surrounded waters of the peninsula. Structures were found on the shoreline area and at depths up to 2-3 and 5-6 metres.

Along the entire northern shore of Nessebar peninsula sections of fortification walls parallel to the shoreline at up to 40 m distance and 1,5 depth were discovered. A bastion, gates, staircase, towers and north-south cross-connections were recorded. The most spectacular structure was the hexagonal tower probably flanking the harbour gate of the classical polis.

On the basis of a complex analysis of the written and epigraphic sources and the data from the archaeological underwater and on land discoveries, several buildings have been identified. All of them were destroyed by the erosion, landslides and earthquakes and nowadays are underwater: the ancient theatre, the temple of Zeus and Hera, the early Christian basilica near the medieval church “St. Georgi Stari”, the northern nave of the basilica “The Virgin Mary Eleousa”, the medieval churches “St. Stefan Akropolit” and Christ Akropolit”. So far there is no evidence of urban extra murus zones around the peninsula.

The partially traced layout of the Messambria-Mesembria fortification walls allows us to conclude that as a result of sea transgression, negative tectonic movements, landslide activity, sea abrasion and seismic activity Nessebar lost a significant part of its historical intramural territory.

A major reason for the intensive destruction of the Nessebar peninsula is its geological substance – a sea terrace with a height of 13-17 m consisting of unstable chalky sandstones, limestone and clay. The rapid abrasion and landslide process were ceased in the late 1980s and 1990s with building of coastal protection facilities, mainly on the northern and eastern side of the peninsula. The underwater archaeological structures in this area remained (after their conservation) under the new road infrastructure. There is a project to mark their layout on the ground and to present them to the visitors. The coastal protection facilities did not affect the underwater archaeological remains east and southeast of the peninsula, where is accessible for ongoing archaeological researches.

Underwater archaeological and geophysical research in 2017

In 2017, the Centre for Underwater Archaeology at the Ministry of Culture resumed the regular archaeological research in Nessebar with funding from the ministry. The main research question which engage the scientists during the next research seasons are: what is the evolution of the landscape of Nessebar peninsula; what part of the ancient town was destroyed by abrasive processes; what are the preserved archaeological structures underwater and what is their age; where were the harbours of the town; what is the state of the structures underwater and what are the possibilities for their exhibition and socialization in order to turn them into a destination for cultural tourism.

In accordance with the funding and the scientific and research questions listed above, in 2017 the CUA conducted a survey in the waters east and south-east of the peninsula, where earlier expeditions have recorded sections of walls, towers and bastions associated by their discoveries with the Thracian town (at depth of 4-5 m, and at a distance of 180 m from the coast), the Greek colony (Classical and Hellenistic Period, at a depth of 4 m and at a distance of 80-130 m from the coast). The research was concentrated in the areas to the east, west and south of the so-called “Southern Pier” (“Yuzhna Buna”) and consisted of geophysical and diving surveys, followed by recording of the discovered archaeological structures. The team of underwater archaeologists and marine geophysicists discovered some of the previously known sections of the town’s fortification system, as well as some structures that are not mentioned in the publications.

Based on the complex geophysical researches of the waters off Nessebar carried out by the CUA, a high-resolution digital terrain model was created. It provided geographical basis for mapping the registered sites as well as guidance for subsequent diving surveys of areas with high archaeological potential. The model will help to understand the logic of the fortification system location, the size of the ancient town as well as the dimensions of its submerged parts.

The results of the underwater archaeological researches were presented in the first joint UNESCO-STAB/ICOMOS Advisory Mission within the framework of the World Heritage Convention and the Convention on the Protection of the Underwater Cultural Heritage. Their experts were invited by the Bulgarian authorities and hosted by the Municipality of Nessebar from 28 November to 3 December 2017.