A sanitary and defence tower. Connected with the castle building by a gallery, the tower served two purposes: it defended the eastern part of the castle walls and was used as a lavatory. Erected on the marsh upon Struga Toruńska banks, Gdanisko survived the demolition of the castle by Toruń burghers in the 15th century. In 1600-1613, on the initiative of Toruń burgomaster Heinrich Stroband, the remains of the castle became a triangular rampart protecting the city from the south, and the tower was transformed into a powder magazine.