On an altitude of 400 meters, the castle is one of the largest of Mani. It was built by the Byzantines in the 15th century, with the purpose of monitoring the passageways to Mani. It was surrounded by a castle in a polygonal shape, with a total length of about 365 meters and a height of 8 to 10 meters. The wall had six towers, and in its middle was a tower with 6 cannons, while 45 more canons were spread throughout the rest of the castle. Two gates allowed access, one northeast and another southwest, and the castle occupied a space of 23,000 square meters. Among the fortifications, there are older ruins of the Hellenistic period, belonging to the acropolis of ancient Gerinia.
The castle was destroyed by the Turks in 1460, along with the church of Saint Nikolaos. A few years later the people of Mani took the castle back, but they lost it in 1670 again to the Turks. During their occupation, the Turks repaired and extended the castle, adding bath houses, a mosque and shops. In 1685, the Venetians seized it, making it the capital of north Mani and the seat of the local Venetian commander. In 1715, the castle fell in the hands of the Turks, and in 1776 it was finally given to the people of Mani.
The castle of Zarnata had an important role in the history of Mani, especially during the Greek Revolution. It was also used during the Greek Civil War, where part of its wall was torn down for the more modern method of fortification with wire fence. The local population used the castle to take refuge during that time.
Entrance is free and access easy.