What Fortress used as a palace and prison has the Festning tunnel running underneath it?
Festning Tunnel The Festning Tunnel (Norwegian: "Festningstunnelen" ) is a motorway tunnel on European Route E18 in the city center of Oslo, Norway. The tunnel has two tubes, with three lanes in each. It runs from Bjørvika, under Akershus Fortress, The City Hall Square and Vika to Filipstad. The tunnel is 1800 m and -45 m elevation at the deepest.
Pfostenschlitzmauer Pfostenschlitzmauer (German for "post-slot wall") is the name for defensive walls protecting Iron Age hill forts and oppida in Central Europe, especially in Bavaria and the Czech Republic. They are characterized by vertical wooden posts set into the front stone facing. The is constructed from a timber lattice filled with earth or rubble. The transverse cross-beams may also protrude through the stone facing, as with the "murus gallicus " used in Gaul and western Germany.