In 1479, a castle was built on an island in the lake by the bishop of TallinnSimon von der Borch. Porkuni castle (German: Borkholm) was a four-sided structure surrounding a central courtyard, where a small church stood. In each corner of the castle stood a cannon-tower, and there was also a gate tower which is still preserved, albeit with a few later alterations. Judging from the remains, the castle was built in different stages and the walls were gradually made higher.[1]