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.
Beylerbeyi Palace Tunnel The Beylerbeyi Palace Tunnel (Turkish: "Beylerbeyi Sarayı Tüneli" ) is a historic tunnel under the Beylerbeyi Palace in Beylerbeyi neighborhood of Üsküdar district in Istanbul, Turkey connecting Üsküdar with Beylerbeyi and Çengelköy.