The castle of Kalamata is built on a low hill at the north-eastern edge of the city, to the east of the river Nedon. The site supervises the fertile plain around Kalamata and the mountain passes to Mt. Taygetus.

Its foundation goes back to the byzantine period; the hill was possibly the site of the acropolis of ancient Pharai. Very few remains of the byzantine phase have survived to this day. Its current state is the result of a major restoration by the Frankish prince Geoffrey I Villehardouin, founder of the principality of Achaea, in the early 13th century. The castle was a heritable feud of the Villehardouin family until 1322. It was the birthplace of the most illustrious of the Frankish rulers, William Villehardouin and his daughter princess Isabella (Izabo), heroine of A. Terzakis’ novel. Around 1430 the castle came under the rule of the Despotate of Mystras and a few years later, in 1460, it fell to the Ottomans. Limited repairs and minor modifications in the fortification were realised during the short-lived second Venetocracy (1685-1715). The relief slab with the lion of St. Mark above the entrance to the outer bailey, is testimony of the Venetian interventions, which must have included the re-building of the gate. The castle was severely damaged in 1825 by the forces of Ibrahim Pasha of Egypt. The monument has the typical form of a byzantine castle, with an inner tower (donjon) at the most remote location of the hill, an inner bailey at the top and a second perimeter encircling the most vulnerable east side. The remains of a church have come to light at the site of the donjon.