In the later stages of World War II, in a former beer cellar in southern Germany, physicists worked frantically at finding a way to split the atom.
The research took place under a 20-metre layer of rock beneath the tiny valley town of Haigerloch, well-concealed and protected from enemy attacks.
As they worked, the scientists assumed that they could be the first in the world to succeed. The fact that they were wrong spared the town from a devastating hail of Allied ordinance.
As it turned out, the United States had already progressed much further than the modest successes of the researchers hidden underground.
Today, the cellar houses a museum that tells the story of the nuclear research once conducted there. A replica of the nuclear reactor – an aluminium chamber around two metres wide – is embedded in the ground.
The team of researchers led by Werner Heisenberg, who was awarded the Nobel Prize for physics in 1932, wanted experimental proof that a chain reaction in a reactor is possible.
They got close, succeeding in splitting nuclei in the giant chamber, but without achieving a self-sustaining chain reaction.
“Their goal was never to build a bomb,” says physicist and Haigerloch museum attendant Egidius Fechter.
Instead, the scientists were thinking more about propulsion for ships with nuclear fission, he says. So why did the researchers go to Haigerloch of all places?
The laboratory had four advantages, says Ernst Seidl director of the Tuebingen University museum.
Its remoteness, its depth within the limestone, the limited relocation effort – the cellar already had a ground-level entrance – and its location directly beneath a church.
During the war, researchers in Germany had to work with the most primitive means, Seidl says.
Information boards on the museum’s walls display details on the researchers – Carl Friedrich von Weizsaecker, Karl Wirtz, Erich Bagge to name just a few. All were avid scientists.
But were they themselves Nazis?
Bagge was a member of the NSDAP party, according to Fechter. As public officials, some of the researchers were forced to become party members, he says, but he wouldn’t want to call them committed Nazis.
After imprisonment in England, many of them worked once more on building up science in Germany, he says.
Fechter grew up in Haigerloch, but for many years he heard nothing about the nuclear cellar in his home town.
“People knew at the end of the war that there was something here, but not what it was,” he says. “They were given various explanations, for instance that they were working on a machine.”
In the late 1970s, celebrations and carnivals were held in the cellar. Only in 1980 was it finally turned into a museum.
The cellar is unique in Germany – there is no other nuclear research facility from this period at its original location, Fechter says.
But this secret laboratory almost led to a catastrophe for the little town. In April 1945, the Allies marched into Haigerloch, discovered the laboratory and wanted to blow up the entire building, Fechter explains.
But at that time the church on the rocks above it was then already more than 300 years old.
The town priest managed to convince the soldiers not to carry the demolition, Fechter says. Nevertheless, they blew up the reactor chamber – its twisted remains can be seen in the museum today.
It later transpired that that the Allies were lenient because they knew about the level of German nuclear research, and that they themselves were much further advanced in this field.
For this reason, the little town was spared a massive bombardment. “It wasn’t worth a sprained ankle to the Allies,” Fechter says.