The Castle of Antimachia is located in the center of the island of Kos, southeast of the village of Antimachia and is a remarkable medieval fortress. The castle was built between 1322 and 1346, and according to the 14th century historical records the castle was also a prison for the convicted knights. The castle is built on the top of a hill overlooking the south coast of Kos. The castle has a triangular shape with a top to the east. Each side of the castle is an independent fortification line, following the formation of the ground. At the entrance there is a massive basilica in the shape of a half-moon with deep loopholes. The castle was renovated by the Knights of St. John in 1494 after a devastating earthquake. The existing walls were reinforced and restored and various types of ramps were constructed along the outer wall. Inside the castle there are remnants of the ancient settlement of Antimachia, many cisterns and two old churches. The settlement was abandoned in 1840.