Sibbesborg Fortress

Sibbesborg Fortress was once located on Storängsholmen Island in the Sipoo estuary. According to more recent research, the fortress was in use for a short time during the reign of Swedish king Albrecht of Mecklenburg in the late 1300s. The castle cannot be dated exactly, and it is unclear who built it and what it was originally called. Since the mid-1800s, the castle has been called Sibbesborg.

The castle was once built on the southern tip of an island located at the mouth of the Sipoo River. Due to land uplift, the island of Borgön is now surrounded by fields, and the bay is about a kilometre away.