Hitler's Secret Tunnels

During WWII, the Nazis built a vast network of secret tunnels all across Europe, not only for movement, but to house top secret projects. Seventy years after the fact, the exact location of all the tunnels are unknown as the Nazis, with defeat imminent nearing what was the end of the war, destroyed all evidence of the tunnels so that the Allied forces would not discover the extent of their secret work. The entrances to many of the tunnels were filled in and documents destroyed, with any known tunnels those the Nazis could not hide before their defeat, and existing maps largely those made by the Allied forces after the war. For modern day explorers Mike Scott and Luke Mahoney, usually focused on treasures of precious metals, the discovery of a map indicating a tunnel system thus far unknown and the associated secrets of the Nazis is too big a lure to ignore. The map, the tunnel system labeled B3c with a code named Jonas, and associated documentation indicate that B3c was of highest priority and that it probably housed some aspect of the Nazis' secret weapons system development. Even if they can authenticate the map and the associated document, locating B3c may not be easy with changes in landmarks, either from natural or man-made forces over the seven decades. But the process may take them in directions they could not even have anticipated.