This is an acropolis of an unfortified settlement, built within the village in the north part of the island at a height of 154 m. There are three construction phases: Hellenistic, Byzantine and Knightly. The south and the east wall of the fortifications (140 m.) are preserved. They are a combination of the Hellenistic fortification, Byzantine walls and chivalric additions. To the northeast there is cylindrical tower, while the semicircular bastion of the castle is a construction of the knightly period. Here you will also see the coat of arms of the Grand Master Emery d'Amboise (1503-1512) and the coat of arms of the Order (1507). The main gate is located in the middle of the eastern wall. Within the fortifications there are three temples: Panagia Kera, Taxiarchi Michael Tharrinos and Megali Panagia. The coat of arms of Grand Master Philibert de Naillac is located in the fort's entrance. Also, here you will find the coats of arms of the Grand Master Jacques de Milly (1454-1461), Antonio Virieu (1456) with the cross of the Order and Grand Master Pedro Raimondo Zacosta (1461-1467) with the coat of arms of the Order. Symi was one of the first islands that fell into the hands of the Knights after the conquest of Rhodes (1306-1309). The repairs made by Naillac (1396-1421) date back to 1407. Florentine explorer Cristoforo Buondelmonti refers to the castle for the first time in 1420. In the period 1454-1461 the castle undergoes reparation, and in 1457 the Turks attack Symi. In 1460 the castle was robbed by the Turks who invaded with 7,000 soldiers. In 1485 and 1504 two new Turkish attacks take place, while in 1522 the island surrendered.