On the picture above is B8 Bergkristall.
A labyrinth of secret underground tunnels believed to have been used by the Nazis to develop a nuclear bomb has been uncovered. The facility, which covers an area of up to 75 acres, was discovered near the town of St Georgen an der Gusen, Austria last week, it has been reported.
Excavations began on the site after researchers detected heightened levels of radiation in the area - supporting claims that the Nazis were developing nuclear weapons.
Documentary maker Andreas Sulzer, who is leading the excavations, told the Sunday Times that the site is 'most likely the biggest secret weapons production facility of the Third Reich'. It is believed to be connected to the B8 Bergkristall underground factory, where the Messerschmitt Me 262 - the first operational jet fighter - was built.
There are also suggestions that the complex is connected to the Mauthausen-Gusen concentration camp.
Its entrance was only uncovered after the excavation team, which includes historians and scientists, pieced together information in declassified intelligence documents and testimonies from witnesses.
The team is now in the process of removing layers of soil and concrete packed into the tunnels and heavy granite plates that were used to cover the entrance. Helmets belonging to SS troops and other Nazi relics are among the items that have been uncovered so far.