During centuries, fortification walls and towers were built to protect ancient Nessebar. The first inhabitants on the peninsula were the Thracians who started to build these walls in the 8th century BC. From this period, a fortified wall and gate were found and can be seen today. After the decay of the Roman Empire, Byzantine rulers started an active construction work in the middle of the 5th century AD. The built walls were in style opus mixtum- an alternation of bricks and stone. Best preserved walls can be seen today near the city gate. The early Byzantine construction system was used in the middle ages as well.
Due to enemy war attacks, part of the walls were destroyed, but then quickly rebuilt. After the Ottoman rule in 1453, the fortification walls lost their significance and strategic importance and were left in ruins.
References:The Château du Lude is one of the many great châteaux of the Loire Valley in France. Le Lude is the most northerly château of the Loire Valley and one of the last important historic castles in France, still inhabited by the same family for the last 260 years. The château is testimony to four centuries of French architecture, as a stronghold transformed into an elegant house during the Renaissance and the 18th century. The monument is located in the valley of Le Loir. Its gardens have evolved throughout the centuries.