Stonehenge is a prehistoric monument in England that was built several thousand years ago. It consists of a circle of extremely heavy, tall rocks that originally came from locations as far as 250 kilometers away. It is unclear how the enormous stones were transported from their distant original locations. However, archaeologists have several theories about how the rocks arrived at Stonehenge.



Boats

One theory is that the rocks were moved by a water route. According to this theory, the rocks were mined or dug out from mountains and transported downhill to the sea. They were then loaded onto simple boat carried them first by sea and then along a river toward the Stonehenge. This is supported by evidence that rocks similar to those at Stonehenge were mined in ancient times from mountains near the sea. Rocks from this kind of location would be relatively easy to roll downhill and then transport by water.



Platform-and-Ball System

Another possibility is that the large rocks were transported using platforms and wooden balls. According to this theory, the large rocks were placed on platforms. Each platform rested on two lines of carved wooden balls. People then pushed the platform, rolling it over the carved balls, all the way to Stonehenge. This idea is supported by an experiment in which archaeology students built their own platform-and-ball system to test the method. It took just seven students to move stones weighing as much as four tons.



Glaciers

Finally, the builders of Stonehenge may not have needed to transport the rocks very far at all. Nature may have done it for them thousands of years before Stonehenge was built. Some researchers believe that ancient glaciers (ice sheets) moving slowly across the land picked up the rocks hundreds of kilometers away and later deposited then much closer to Stonehenge. This theory is supported by the fact that glaciers have moved large rocks in many other places.