While searching around in the basement of the The Golden Gate the team found an old iron door that was inscribed with a crest from the time of the Kaisers.
This door lead onto a tunnel that formed part of the sewer system of Berlin. On the side of the tunnel there was a walkway that had obviously been deliberately constructed to allow people to move about underground.
In exploring the tunnel they discovered that it was part of a network that run under the government district of the city. While looking much older and being blocked in places from bomb damage it connected a number of important buildings and some lesser ones. There were a load of signs from the war era pointing out the main government and party buildings.