Secret Nazi nuclear weapons testing bunker unearthed in Austria

The secret weapons complex was found near Mauthausen-Gusen concentration camp in Austria

An underground weapons bunker built by Nazis to test nuclear and chemical weapons has been unearthed in Austria.
It was built using slave labor from the nearby Mauthausen-Gusen concentration camp. Austrian documentary filmmaker Andreas Sulzer noticed a reference to the subterranean site in the diary of an Austrian physicist recruited by the Nazis. The stronghold was located near the town of Sankt Georgen an der Gusen, and not far from the Bergkristall factory where the first operational jet-powered fighter, the Messerschmitt Me 262, was invented. Footage from the previously-unearthed Bergkristall site is below.

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From The Independent:

Its exact location was determined using intelligence reports and radiation tests, which revealed higher than normal levels of radioactivity.
Andreas Sulzer, the filmmaker who is leading the exploration, discovered a critical 1944 report by the forerunner to the CIA, from an American spy who noted the existence of a secret weapons program in the area.

Sulzer told the Sunday Times, “Prisoners from concentration camps across Europe were handpicked for their special skills--physicists, chemists or other experts--to work on this monstrous project and we owe it to the victims to finally open the site and reveal the truth.”
From the International Business Times:
It is believed that an estimated 320,000 inmates died building the labyrinth of concrete tunnels and shafts.
It is believed to be the location of a secret weapons programme, led by SS General Hans Kammler. Kammler is thought to have lived on the site during the war. Rumours continue to surround his death, with some suggesting he was given a new identity by the US government in exchange for details on Nazi weapons research.
The deadly V-2 rocket which struck at London during the final months of the World War II was tested at the complex. It is also thought that scientists experimented with the use of radioactive material and chemical gas.