article_snippet: The OAP treasure hunters are digging beneath the streets of the old industrial city of Wuppertal.
article_snippet: Dozens of theories have been put forward for Dozens of theories whereabouts and in some cases, millions spent trying to unearth the treasure, but as yet nothing has been found.
article_snippet: The Puzzle of Poppen Wood' by Mario Ulbrich unleashed a fresh wave of treasure hunters who arrived at weekends with shovels, metals detectors and vast reserves of optimism to scour for the artwork.
article_snippet: As he probed into the history of the cannons he discovered plans for secret underground workings.
article_snippet: It vanished off of maps after World War Two but in March 2011 he and Gluba managed to find a ventilation shaft that leads down into a subterranean structure he and Gluba believe is the old shelter.
article_snippet: It is the most dangerous of the hunting grounds and draws scores of illegal searchers every weekend.
article_snippet: It is a tunnel system many miles in length with thousands of caves, bunkers and storerooms.
article_snippet: Both above and below ground, the area is littered with shells and bombs big enough to destroy a city block.
article_snippet: At weekends authorities play cat-and-mouse with the treasure hunters who enter the sealed-off area illegally in ones and twos - and sometimes in mini-bus groups - armed with metal detectors and a belief in the stories.
highlights_snippet: Now team of OAPs claim to have proof Its fate is hidden under city of Wuppertal .