The biggest of Stonehenge’s stones, known as sarsens, are up to 30 feet (9 meters) tall and weigh 25 tons (22.6 metric tons) on average. It is widely believed that they were brought from Marlborough Downs, a distance of 20 miles (32 kilometers) to the north.
Smaller stones, referred to as “bluestones” (they have a bluish tinge when wet or freshly broken), weigh up to 4 tons and come from several different sites in western Wales, having been transported as far as 140 miles (225 km). It’s unknown how people in antiquity moved them that far. Scientists have raised the possibility that during the last ice age glaciers carried these bluestones closer to the Stonehenge area and the monument’s makers didn’t have to move them all the way from Wales. Water transport through raft is another idea that has been proposed but researchers now question whether this method was viable.