Eskihisar Castle is located in the village of the same name in Kocaeli Province. It was first mentioned in 1241 as a Byzantine fortification, and its inner walls were built by Emperor Manuel I Komnenos in the second part of the twelfth century, and the Byzantine Emperor John III Doukas Vatazis built the walls The curtains of the inner castle were built in 1241, and the outer walls and towers in the southeast corner were built during the reign of Emperor Andronikos II Paleologos around 1300.