But it also made the progress of digging tunnels was slow.
Thousands of forced labor from camps across the Soviet Union and Poland helped build the tunnel.
They worked in appalling conditions, exhausted and starving.
Some 5,000 slave labors died in this project.
They are all of a similar design, corresponding to the layout of other subterranean Fuhrer Headquarters.
Three of these sites are run by private owners and can be visited by tourists.
Only when one enters the tunnels, the true scope of this unrealistic construction project becomes obvious.
Indeed, Riese means giant.
The car in this photograph should give you an idea of how massive some of the tunnels are.
Photo credit:Przykuta/Wikimedia
Photo credit:Aneta Pawska/Wikimedia
Photo credit:Ministry of Foreign Affairs, Poland
