Remains of a small castle and four ruined churches of the Francocracy (Frankish period) are preserved on a low hill east of Achladochori, at the location called Palaiopyrgas. They are remnants of an extensive settlement, as suggested by the scattered pot sherds of utilitarian vessels dated to the late antiquity and of the medieval period. The most likely identification is with the medieval village Kosmena or Kosmina, referred to in archival texts of the 14th and 15th centuries. The castle walls follow the contour lines and the site commands the largest part of the Pylia peninsula’s eastern coastline.

The preservation of the outer fortification is very bad. The wall has mostly collapsed. The only surviving section is the lower part of a large orthogonal tower at the north-western corner of the castle. A similar tower must have existed at the south-western corner. The entrance gate was probably opened at the northern side, east of the tower. House remains are visible inside the enceinte. A barrel-vaulted cistern with an orthogonal mouth is preserved southwest of the castle.