The large village Büyükkale (big fortress) is located in the Kaystros Valley 6.8 km northeast east of Halkapınar. Remains of a citadel are preserved on a steep rocky knoll west of the village Büyükkale Bucaği. No excavations have been conducted so far. The citadel consists of an upper part and a lower ring-shaped external Hellenistic fortification wall along the foothill. Only on the western and northern side of the wall have larger pieces of Cyclopean masonry survived. Recep Meriç argues that the wall dates to Late Bronze Age. He found a rim of a Late Bronze Age vessel.