At the south edge of Methoni Castle a fortified islet floats. Bourtzi - as it is called - was built in the1500’s by the Venetians and is connected to the Sea Gate of the castle with a paved tiny road. At various times it was used as a fort, a prison, a lighthouse, and a refuge during periods of raids.

Bourtzi consists of an octagonal tower, which is surrounded by a low octagonal wall. The tower is built on two levels and is covered with a semi-cylindrical dome. A four-sided cistern occupies its ground floor.