What Fortress used as a palace and prison has the Festning tunnel running underneath it?
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. It has also been used as a palace and as a prison.
Berlin Fortress The Berlin Fortress (German "Festung Berlin") was the fortification of the historic city of Berlin. Construction started in 1650. The demolition of its ramparts began in 1740.