Built around 1300, Akershus Fortress (aka Akershus Castle) is a medieval castle that served as a defensive stronghold for the city of Oslo. It has served as a prison during the late 18th-19th centuries, with many prisoners dying during their imprisonment. Nazi's also occupied the castle during World War II, carrying out many executions on the site.
Akershus Castle is believed to be the most haunted place in Norway, with many ghosts to speak of. With its vast history it's of little surprise. The most popular of all is the demon dog named Malcanisen that's said to guard the gates to the castle. Legend says that anyone that is approached by Malcanisen is sentenced to a horrible death sometime in the following three months.
The ghost of a woman named Mantelgeisten is often seen within the castle, walking back towards her chamber. She appears from the darkness wearing a long robe, and has no facial features.