A natural fortified hill stands over three gulfs: Skala, Merika and Chochlaka. There laid the acropolis – the most significant pre-Christian monument of Patmos. Shells in superficial layers and stone tools made of obsidian and firestone, all discovered in the area, prove the existence of the settlement since the Bronze Age. Many findings dating back to the geometric, classic, Hellenistic and even the Roman period, demonstrate the continuous use of the hill throughout history. In Kastelli, you can still see impressive remains of walls dating back to the end of the classical period (late 4th century BC). Quite extensive and high parts of the fortification, with good masonry, as well as rectangular towers are still standing tall. One of the towers still preserves its staircase and entrance gate. The settlement lay probably to the east of the acropolis.
Between 2001 and 2002 the 22nd Ephorate of Prehistoric and Classical Antiquities funded by the Ministry of the Aegean performed cleaning and topographic survey procedures in the ancient acropolis. Moveable findings, mainly pottery and small metal objects from the area are on display in the Nikolaidis Mansion at Chora.