The castle of Methoni is the most important in Greece. It was built by the Venetians when they became masters of the town in 1209 AD. It is built on a rock that goes into the sea and is separated from the mainland by an artificial moat. It has an area of 93 acres. On the north side there is a gate which is made of rectangular limestone. The castle walls are reinforced at some points by towers. The Bourtzi tower lies at the south of the fortress, built on an islet south of the castle. It is connected to the main fortress by a bridge with arches. Bourtzi became part of the maritime fortification of Methoni and served various purposes per seasons: it was used as the base of the guard for the port control, as a lighthouse, as a prison, but also as a refuge in times of residents siege.
On the east side of the castle there is a small breakwater which today is part of the small port of Methoni.