Situated on a small peninsula linked with the mainland by a narrow 400 m long isthmus. A port in Thracian times, at the end of the 6th century B.C. the Dorian Greeks turned it into a lively trade center while preserving its Thracian name of Mesambria.

A large part of the ancient town has been irreversibly destroyed - the originally some 40 ha large peninsula is a mere 24 ha today.

Dating back to the 12th-6th century B.C. are a gate and the now submerged remains of the town's former fortifications. Other remains include the ruins of fortress walls and carved limestone towers, archaeological remnants of the agora in the center, of the acropolis, of an ancient temple, of the peristyle and of several dwellings.

Unaffected by Roman rule, the town existed independently before it became part of Byzantium, together with the entire Balkan Peninsula. The most important monument surviving from Byzantine times is the St. Sophia basilica, also known as the Old Metropolitan (rising in the place of an ancient agora).

Within the boundaries of the Bulgarian state during the 13th and 14th century, when the country was at its strongest both politically and economically, experiencing a cultural upsurge, Nessebur was a town of 40 churches (built during the 11th to 14th century). Preserved until the present of these are: the New Metropolitan - St. Stefan, St. John the Baptist, St. Todor, St. Paraskeva, Chtist Pantocrator, St. John Aliturgetos, and the Sts. Arcangels Michael and Gabriel church.

The New Metropolitan or St. Stefan (11th c.) is one of the last representatives of basilicas in medieval Bulgaria with perfectly preserved murals dated 1593 and 1599. some of the compositions are influenced by Italian painting but maritime themes and subjects are nevertheless characteristic.

St. John the Baptist (10th-11th c.) represents the transition between a basilica and a cross-domed church.

Christ Pantocrator is one of the best preserved medieval churches in Bulgaria. The exterior facades are decorated with colourful ceramics depicting different motifs.

Similar in shape but with richer decoration and sculptures is the St. John Aliturgetos church. Its facades are intricately broken by pilasters and arches, with rhythmically alternating white stone and red bricks.

The Sts. Archangels church has extremely picturesque facades with two rows of decorative blind arches, the upper row being broken by large semi-circular gables.

On the whole, the mediaeval Nessebur churches are characterized by intricate decorative elements and combinations of stone and bricks, by immured glazed ceramic discs and four-leaved rosettes. Niches, consoles and arcades also break the facades.

The houses, which lend their peculiar 19th century air to present-day Nessebur, were built during the Bulgarian National revival Period. The typical 18th-19th century Nessebur house have small yards facing the street, which is demarcated by the walls of the lower floors and fences. A wooden staircase leads up to the second floor, which is lightly structured and completely faced with wood. The overhanging roof eaves serve to optically narrow the streets still further. The central living quarters are occupied by the parlour from which numerous doors lead to the remaining rooms. Wooden ceilings and whitewashed walls characterize the interior. The upper-floor windows are wide, those on the ground floor are narrow and few in number. The Ivan Markov, Pipcherkov, Capt. Pavel, Bogotov, Zhelyu Bogdanov, Lambrinov, Toulev, Diamandiev, Hadjitraev, Hristo Kochev and Muskoyannis houses are all worth seeing. The Lambrinov and Muskoyannis houses, in particular, have richly decorated facades and interiors.

Nessebur's intransient value and its centuries-old cultural wealth have gained due recognition with its inclusion in the List of World Cultural Heritage in 1983.