Tunnels dug by Nazi Germany in the Slovenian city of Maribor at the end of 1943 for protection against air raids by the Allies have become an increasingly popular tourist sight since they were opened to the public two years ago.

The tunnels were made when the Nazis launched a Luftfahrtwerke Steiermar aircraft engine factory in the city they occupied two days after invading Yugoslavia on 6 April 1941.

Covering over 8,500 square metres, the tunnels came to light two years ago and is now one of the largest tourist attractions in the area.

An important industrial city, Maribor was often bombed by the Allies, so the Nazis decided in 1944 to produce aircraft engines underground.

“What attracts visitors is the mystery surrounding the tunnels. There are many urban myths, for example, that tunnels could lead to Kintrichevo (a town 25 kilometres away), but this has not yet been proven,” tour guide Barbara Islacar told the STA news agency.