After World War II was finally over and the full truth of the Nazis’ atrocities was revealed to all, the question of “what if they actually won?” haunted the world for decades to come. This grim hypothesis has been the source of historical discussions, works of fiction, and many legislative measures to prevent a similar regime from coming to power

But for Andreas Sulzer, this is more than just speculative fiction. The filmmaker recently led the discovery of a hidden underground factory where the Nazis performed their own research, and what they found is too terrifying for words.

St. Georgen an der Gusen in Austria may seem like a nice, quiet town. You would never imagine the unseen horrors that lie within it.

During World War II, many thousands of Jews were methodically slaughtered in the town’s Mathausen-Gusen concentration camp.

The prisoners of the camp were given a much-needed moment of relief and joy when the allied soldiers liberated them. These prisoners were forced to build underground catacombs that made up the B8 Bergkristall weapons facility as well as an additional area that worked with nuclear fusion to build the Nazis’ own version of the atomic bomb.

A single guard tower still stands over the Mathausen-Gusen concentration camp, a stern reminder of what happens when humanity reaches the darkest pits of evil. 

This is what Mathausen-Gusen looked like right after the allies liberated it in May of 1945. It may be empty, but the horror of what happened here is still palpable.

As it became abundantly clear that the odds of winning the war were not in their favor, the Nazis built these tunnels in a desperate attempt to preserve their classified weapons facility. Huge granite plates were even used to barricade the entrances, so that even after the war ended, the SS’s terrible operation would remain hidden.

Andreas Sulzer brought in an excavation crew to help him break into the underground tunnels that the prisoners were forced to build. This complex series of channels shed new light on the twisted laboratories that were used by Hitler’s scientists to research atomic weaponry.

A letter written by Viktor Schauberger regarding his covert research into “atom-smashing” sparked Sulzer’s interest in this project, as did some fascinating documents from a high-ranking American agent that had been paying close attention to the scientists of the SS.

According to these documents, a complex and vital building was hidden beneath the surface of St. Georgen. After three years of determined excavation, Sulzer’s team of scientists and historians found many artifacts, including this Nazi helmet. 

A high-ranking SS officer named Hans Kammler was put in charge of the Mathausen-Gusen concentration camp, officially approving of each gas chamber’s blueprints. He even watched over the prisoners’ work on Messerschmitt ME 262, the first jet engine-powered airplane, in the secret B8 Bergkristall weapons factory. Until the Allies developed their own jet-powered airplanes, this was the fastest airplane in the world. He was also in charge of Hitler’s missile program.

Franz Ziereis, SS Commander of Mathausen-Gusen, is in the center of this photo. He may have hidden mass graves within the camp’s catacombs, according to Sulzer and his team. Ziereis was shot by Allied soldiers while attempting to flee the facility, then interrogated before his death. Clearly, he had something to hide.

On his deathbed, Ziereis revealed that he had been ordered to kill the prisoners of the facility using an explosive chemical substance — in particular, the ones working on the secret Nazi projects. He claimed that he didn’t carry out the order, but the 320,000 captives that died due to the camp’s horrible conditions may tell a different story.

With tunnels running 75 acres, this facility is massive. Ground-penetrating radar was needed to measure the enormous scale of the factory.

The Nazis were proud of the mere existence of this facility. Heinrich Himmler, the head of the SS, visited it several times during the war. The Third Reich prized this facility too much to allow their enemies to ever get a hold of it.

Sulzer’s crew broke through the concrete and granite with heavy machinery. Considering the lengths that the SS went to to make sure the facility never got discovered, this was not an easy task.

Weapons development, including, perhaps, atomic bomb research, was held in these tight, shadowy tunnels. Prisoners with particular skills, such as rocket scientists, physicists, and chemists, were forced to help build these unfathomably deadly weapons.

Even before the weapons development started, though, thousands of prisoners died in the process of building the tunnels. The bodies of the prisoners killed before the Allied liberation may still be somewhere within these tunnels.

The tunnels were intentionally built deep underground to protect them from bombings.

Watch Sulzer’s findings below for even more eerie images of Mathausen-Gusen.

As painful as it is to think about what happened in this horrifying facility, we must honor the people who suffered at the hands of such unimaginable cruelty by continuing to support Sulzer’s project and exposing the world to his team’s discoveries. We must never forget the atrocities of the Holocaust.