Kummakivi or “Strange Rock” can be found in the forests of Finland. These strange geological formation have, without any scientific explanation, wound up in a perplexing positions. The mystifying sight is that of a giant rock performing an unbelievable balancing act on a seemingly smooth, curved mound.
Some Finnish folklore explains the odd locations of these giant stones by saying that trolls (or giants) carried, threw or rolled them there.
Or glaciers. Probably that rather than trolls. But then, I'm not living in Scandinavia, where trolls do in fact exist.