These tunnels were once believed to hide religious fortunes deep in their chambers, but the real treasure is found in who - or what - created them.  

In 2009, a farmer was driving through his corn field in the south of Brazil when he suddenly felt his tractor sink and lurch to one side, making the vehicle shudder to a halt.  

Researchers came to investigate and were surprised to find a tunnel nearly 2m high by almost 2m wide and about 15m long running across the field and right under the farmer's house. 

Deep claw marks embedded into the walls indicated its past occupant was not human.  A geologist and one of the scientists who visited the farmer's property, concluded was the work of a giant ground sloth from at least 10,000 years ago.