Towns that disappear, towns that change, towns that go on. The transition from the ancient to the medieval world

The changes that marked the transition from the ancient to the medieval world did not happen all at once. On the contrary, they constituted a transformation, a gradual process, quite substantial in nature, which also had an effect on the monuments. Across the Byzantine world, following a period of contraction and decline during the 7th and 8th centuries, known as the 'dark ages', there followed a period of recovery in the great cities of the empire. Instead of the great urban centres of ancient times and the early Byzantine period, the cities transformed into fortified settlements, the so-called city-castles. In other words, the form of the ancient city was abandoned in favour of a transformation into a settlement that was delineated and protected by walls. The urban centres became places of safe inhabitation. The city-forts, were clearly smaller and arranged differently, marked by the absence of a town plan or organisation of spaces and buildings. There was a noticeable abandonment of coastal positions after the 6th century.
A common characteristic of this period was the gradual domination of the new religion, Christianity. New churches were built, the basilicas, which often mark the centre of the towns, and which, together with the administrative and military buildings, were the expression of communal or public services.
Changes took place in important ancient towns in Euboea and Boeotia. Some ancient towns remained in occupation, on the same sites, and kept their ancient names (Thebes, Karystos, Eretria). Other towns were abandoned in the search for safer positions.