The archives of Patmos provide the first information about the castle and the medieval village of Old Pyli which are located in the area modern of Amani, at central Kos.

Specifically, the edict of Alexios I Komnenos in March 1085, confirms the donation of two site on the island to Christodoulos Latrinos, founder of the Monastery of St John the Theologian in Patmos, and their tax exemption. Christodoulos founded the Monastery of Theotokos, also known as Panagia Kastrianon. In 1088 the area of ​​Pyli accrues to the Byzantine state as part of the estate of Christodoulos, and in return the monk was granted the island of Patmos. In 1493 the castle of Old Pyli, an important refuge for the population from the Ottoman invasions that occurred during the Knights' period, was severely damadged by a powerful earthquake. One of the events related to the castle occurred in 1526, during the uprising of the inhabitants against the Ottoman administration, when Christian locals massacred Muslims and then barricaded the castle. The Castle was reportedly abandoned after the epidemic of the early 19th century.

Traces the Cyclopean walls on the NW side and ceramic finds from the Bronze Age attest the prehistoric occupation of the site. The medieval fortifications of the 11th century strengthened and expanded its naturally fortified position with new enclosures. The first, upper enclosure surrounds the hilltop, while the second defines a greater area to the east, west and south side of the first. Traces of walls and a gate to the north side of the enclosure and suggest that this area was also walled. Access to the castle is gained through the three surviving gates, which facilitate communication between the enclosures. Seven towers, four in the first and three in the second enclosure, strengthened the fortifications, despite the inadequate and flimsy construction which was dictated by the circumstances of the time. The fragmented architectural remains inside the castle belong mostly to the period of Ottoman rule. Among these there are two buildings and an underground cistern located inside the first enclosure, buttress walls and unidentified buildings in the second, and a small building with square plan and a conch-probably a chapel- in the fourth enclosure.