The tunnels, lying about 50 feet below Tiergarten Park, were part of a vast underground network that would have included roads and a rail system. Above the surface, a series of huge buildings, which were never completed due to World War II.
The city, which has since been dubbed “Germania,” would have far outshined the architecture of cities like Paris and Rome, with its center being the biggest domed hall in history.
The three enormous tunnels normally closed to the public due to safety, were recently opened under Berlin, giving a taste of Adolf Hitler's megalomaniac vision of a new centre for the capital of Nazi Germany. Tours need to be arranged in advance.
The overground plans, never completed because of World War Two, included boulevards, squares and huge buildings, such as an arch dwarfing the Arc de Triomphe in Paris, and the 290-metre high Great Hall, with room for 180,000 people. These splendous and architecturally rich buildings were designed by Nazi architect Albert Speer, including the biggest domed hall the world had ever seen. 16 meter (50 foot) tunnels including a transport network, were constructed in 1938 as part of an underground transport network beneath the planned city.
"The tunnels -- which are in surprisingly good condition -- were part of Speer's grand plans, what we now call 'Germania'," historian Dietmar Arnold, head of the Berlin Underground Association and bunker tour guide, told Reuters.
Last week, Arnold -- who runs an exhibition of Hitler's plans -- took journalists on a rare visit into the dank tunnels.
"The acoustics are incredible," said Arnold, who likes singing a note and hearing it reverberate around him.