Oslo - Akershus Fortress
Akershus Fortress or Akershus Festning is a medieval castle that was built to protect Oslo. It was constructed in response to the Norwegian nobleman, Earl Alv Erlingsson of Sarpsborg's earlier attack on Oslo. Akershus has also been a prison, a section of it known as The Slavery as the prisoners could be rented out for work in the city. It has housed many rebels and criminals through Norwegian history.