The castle of Zarnata is located on a low hill between the villages Kampos and Stavropigio, in a prominent location that offers command of the coastline and the passes to the hinterland of Mani. Large parts of its perimeter have been founded over the ruins of a hellenistic fortification, which has been identified as the acropolis of ancient Gerineia. The castle was probably built in the first half of the 15th century. Its medieval remains bear strong resemblance with the masonry of the small church of Agios Nikolaos, within the enceinte. The church’s first layer of wall paintings dates to the mid 15th century.

The castle was conquered in 1670 by the Ottomans, who rebuilt it and gave it its current appearance. The wall is partially preserved; it is vertical and it follows the natural contour lines, as well as the outline of the ancient fortification. In many places it rises above three meters. Round and rectangular towers have been built in various positions; three of them survive to this day. On top of the hill stands a late 18th century fortified complex consisting of a house and a three-storey defensive tower. They were owned by the local rulers, Koutifaris and Koumoundouros. In 1780 the cross-vaulted church of Zoodochos Pigi (Life-giving Spring) was built inside the castle and it was decorated in 1787.