Originally an ancient place of execution, it saw the construction of a Benedictine monastery just after the year 1000. This was probably one of the first two in Scandinavia. In 1658 it was made into a fortress and prison, later becoming a custom station. The most famous inmate was the Danish Count Peder Griffenfeld, who was imprisoned here for 18 years. A boat trip on the beautiful Trondheimsfjord is an experience in itself, where you can see the city from the sea. And a visit to the fortress on the island will take you thousands of years back in time.