Wikipedia: "Old Elbe Tunnel or St. Pauli Elbe Tunnel (German: Alter Elbtunnel (coll.) or St. Pauli Elbtunnel (official name)) (opened 1911), is a pedestrian and vehicle tunnel in Hamburg Germany. The 426 m (1,398 ft) long tunnel was a technical sensation; 24 m (80 ft) beneath the surface, two tubes with 6 m (20 ft) diameter connect central Hamburg with the docks and shipyards on the south side of the river Elbe This meant a big improvement for tens of thousands of workers in one of the busiest harbours in the world.
Hamburg: Second largest city of Germany, situated in the north at the river Elbe, because of the seaport well known as a city of merchants. Because of the nearby sea, you will always have some fresh breeze while you are walking through the streets with nice private town-houses or while you are floating along aboard an “Alsterdampfer” on the river Alster.