Old Elbe Tunnel or St. Pauli Elbe Tunnel which opened in 1911, is a pedestrian and vehicle tunnel in Hamburg, Germany. The 426 m long tunnel was a technical sensation; 24 m beneath the surface, two 6 m diameter tubes connect central Hamburg with the docks and shipyards on the south side of the river Elbe. This was a big improvement for tens of thousands of workers in one of the busiest harbors in the world. Four large lifts on either side of the tunnel carry pedestrians and vehicles to the bottom. The two tunnels are both still in operation, though due to their limited capacity by today’s standards, other bridges and tunnels have been built and taken over most of the traffic. In 2008 approximately 300,000 cars, 63,000 bicycles, and 700,000 pedestrians used the tunnel. The tunnel is opened 24 hours for pedestrians and bicycles. For motorized vehicles, opening times are currently Monday to Friday from 5:20 AM to 8:00 PM and on Saturdays from 5:20 AM to 4:00 PM.

More details: https://en.wikipedia.org/wiki/Elbe_Tunnel_%281911%29