Stonehenge, a rock circle, is not only one of Britain's most famous historical places but also one of its greatest mysteries.
Every year it receives more than 750,000 visitors.
People like to go to this place especially in June as they want to see the sun rising on the longest day of the year.
For many years, historians believed Stonehenge was a temple where ancient leaders tried to communicate with the gods.
However, historian Paul Stoker thinks this can't be true because Stonehenge was built so many centuries ago.
"The leaders arrived in England much later," he points out.
Another popular idea is that Stonehenge might be a kind of calendar.
The large stones were put together in a certain way.
On midsummers morning, the sun shines directly into the center of the stones.
Other people believe the stones have a medical purpose.
They think the stones can prevent illness and keep people healthy.
"As you walk there, you can feel the energy from your feet move up your body,"said one visitor.
No one is sure what Stonehenge was used for,
but most agree that the position of the stones must be for a special purpose.
Some think it might be a burial place or a place to honor ancestors.
Others think it was built to celebrate a victory over an enemy.
Stonehenge was built slowly over a long period of time.
Most historians believe it must be almost 5,000 years old.
One of the greatest mysteries is how it was built because the stones are so big and heavy.
In 2001, a group of English volunteers tried to build another Stonehenge,
but they couldn't.
"we don't really know who built Stonehenge," says Paul Stoker.
"And perhaps we might never know, but we do know they must have been hard-working — and great planners!"