Is There a Giant Causeway?

In many parts of the world, you'll find enormous boulders without other similar rocks around them. The scientific explanation for them is that they were carried from their original location to their current location by glaciers during one of the ice ages. But what are you to make of this if you're living before the scientific revolution and you don't know about ice ages? How are you to explain why there's a giant immovable rock sitting out in your field?