Stonehenge is an ancient monument that is located on Salisbury Plain in Wiltshire, Southern England. The United Nations declared it a World Heritage Site in 1986.

Stonehenge was built in three phases, beginning more than 5,000 years ago. About 3100 BC, several logs were placed on end in a circle and surrounded by a wide ditch. Archeologists believe the ditch was dug using animal antlers.

About 2500 BC, it was rebuilt with stones, called bluestones, from South Wales, more than 245 miles (394 kilometers) away. These stones, each weighing 4 to 5 tons (3,600 to 4,500 kilograms), were likely dragged to the sea, placed on large rafts, and floated down the coast and then upriver. From there, they were dragged overland to Salisbury Plain.

About 2300 BC, the bluestones were rearranged and even bigger stones, some weighing up to 45 tons (40,000 kilograms), were brought from 20 miles (32 kilometers) away. Thirty massive sandstones, each about 13 feet (4 meters) high, were stood on end about three to four feet (one meter) apart in a large circle. Heavy rectangular stones were placed on top of them and fitted together using woodworking methods. This continuous circle of stone around the top makes Stonehenge special.

Modern scientists believe that three different groups of prehistoric people built Stonehenge. It was a tremendous engineering achievement, and thousands of people would have worked on it.

No one knows for sure why Stonehenge was built on Salisbury Plain or for what purpose. It may have been a temple, a place to watch the movement of the sun and stars, a burial place for high-ranking people, or all three. Hundreds of burial mounds surround it.

Today, only about half of the original monument exists. In later centuries, many of the stones were used to build homes or roads. People continued to chip off parts of the stones until the 1970s. To stop the damage, since 1978, Stonehenge can only be viewed from a distance.