Stonehenge is a massive stone monument located on a chalky plain north of the modern-day city of Salisbury, England. Research shows that the site has continuously evolved over about 10,000 years. The structure that we call "Stonehenge" was built between roughly 5,000 and 4,000 years ago and was once part of a larger sacred landscape that included a massive stone monument that was 15 times the size of Stonehenge.
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. Recent experiments show that it is possible for a one-ton stone to be moved by a dozen people on a wooden trackway, but whether this technique was actually used by the ancient builders is uncertain.