Trakai Island Castle

Trakai Island Castle is an island castle located in Trakai, Lithuania, on an island in Lake Galvė. The construction of the stone castle was begun in the 14th century by Kęstutis, and around 1409 major works were completed by his son Vytautas the Great, who died in this castle in 1430. Trakai was one of the main centers of the Grand Duchy of Lithuania and the castle held great strategic importance. In Eastern Europe it is the only island castle.
Trakai Island Castle was built in several phases. During the first phase, in the second half of the 14th century, the castle was constructed on the largest of three lake islands by the order of Grand Duke Kęstutis. The construction of Trakai Island Castle was related to the expansion and strengthening of the Trakai Peninsula Castle. Kęstutis moved his main residence and his treasury to the Island Castle.

Wikipedia