Geology shows that the Altar Stone at Stonehenge wasn’t local, and didn’t come from Wales either, as once thought. It’s red sandstone, which means it must have come from somewhere between Orkney and Inverness. (See map.)

Since some of the people who built Stonehenge came from Orkney, that’s been the best guess so far. But Orkney has now been ruled out.

No lorries, no railways, no cranes – how did they move it such a distance?