The Mylopotamos fortress is one of the three fortresses dating back to the Venetian domination, located near the village of Mylopotamos on the western side of Kythira. It is a Venetian fortress built during the 15th century (as attested by the frescos in the churches) to protect the occupants of the area and to guard the western shores of the island. It was rebuilt and reinforced in 1565, a few years after the raid of by Hayreddin Barbarossa the chief admiral of the Ottoman fleet in Agios Dimitrios (Paliochora).
In the fortress one can walk through the main street bordered by several houses still in a good condition, and nine churches, decorated with Byzantine and post-Byzantine frescos. The winged Lion of Saint Marco, emblem of the Republic of Venice stands on the castle’s gate. The lion holds a book with the inscription: “PAX TIBI MARCE EVANGELISTA MEUS, MDLXV (Peace to you Evangelist Marco, 1565).
The houses inside the fortress were usually two-floor houses, with the ground floor showing a vaulted roof and the first floor being covered by a flat roof. Access to the upper floor was via an outside staircase. The churches were built during the 16th and 17th century and include Panagia Mesoporitissa, Profitis Ilias, Agios Athanasios, Agios Ioannis Theologos, Agioi Pantes, Agios Ioannis Prodromos, Chrystomos and Metamorfosi. The settlement was occupied until the 1950s.