20,000 years ago the eastern Denmark and all of Sweden and Norway were covered by a giant glacier. The glacier began its life in the fells of Norway, where the snow did not melt during the summer. On the contrary, there came more and more snow, which at the bottom was compressed into clear ice.
The enormous weight from the increasing amount of snow and ice on top of the glacier made the bottom ice gel-like and it started to move downwards and forward. It spred out, while it transported rocks, boulders, and gravel all the way to Denmark.
Giant rocks was transported by the ice and left as beached whales. Many of these rocks was used by people for prehistoric graves and other constructions, and ‘wild rocks’ have eventually become rare.