The Danish culture agency - Kulturstyrelsen - initially thought the application by Viborg Museum was a joke, the Copenhagen Post reports . But after realizing the idea was legitimate they approved it. Now the velvety creatures are being to be used at a site south of Viborg, where archaeologists believe the remains of a fort from the Middle Ages lie hidden beneath the surface. The museum analyses the contents of mole hills that the animals leave behind after burrowing - the moles' "finds" help archaeologists work out where buildings are located underground. Jesper Hjermind, the archaeologist who came up with the idea, says it's based on moles bringing bits of pottery and other items to the surface. "The closer we get to a building, the higher the content of items per litre we find," he says. "It's simple, but it works."