Axel Nicolai Herlofson was imprisoned in which medieval castle near Oslo, Norway?
Axel Nicolai Herlofson:  He attempted to flee the country, but was arrested in the last minute and sentenced to six years imprisonment with hard labour, which he served in Norway's strictest prison at Akershus Fortress. Akershus Fortress: Akershus Fortress (Norwegian: "Akershus Festning" ) or Akershus Castle (Norwegian: "Akershus slott" ) is a medieval castle that was built to protect Oslo, the capital of Norway.
Akershus Fortress