One of the world's most famous monuments, the enormous standing rocks at Stonehenge have confused and fascinated visitors for thousands of years.
If you've never visited the site up close, it can be hard to imagine just how impressive it is. Each of the standing stones, which once formed a full ring, are 13 feet high and almost 7 feet wide. They weigh up to 25 tonnes each, and the sheer size of the monument has raised a lot of questions.
Why was Stonehenge built?
Even after hundreds of years of intense research, experts still can't say for sure what Stonehenge was used for. It was built at least 4,000 years ago, but could date back as far as the year 3000 B.C.
We know for sure that the site was used as a burial ground, because there are hundreds of graves in and around the site. Experts say that wealthy and important families may have reserved the site as a primitive cemetery.
But there is also evidence that Stonehenge was built as part of a Pagan ritual. And the points between the rocks mark places where the sun and moon rise and set, revealing it could have been an "ancient observatory."
But the real question is how were these massive blocks moved into place? A surprising source may have the answer...