Built in 1911 these two tunnels run under the River Elbe. These things were engineering genius back in the day, 4 giant lifts either side each able to carry two cars drop you through the ground 24m down. Its open 24/7 to pedestrians and I managed to head there at 11pm one night when no one was around. lets just say it's only a little scary being in a 426m long tunnel by yourself.