Stonehenge was built in four stages and although archaeologists do not know for certain how long it took to build, it is assumed that it took about 1,500 years to complete. Stonehenge was completed around 3,500 years ago.
The first stage of Stonehenge's construction began around 3100 B.C. At that time, the constructors dug round holes, called Aubrey holes, in the chalk. Scientists have discovered human remains in many of the holes, although they believe the holes were originally intended for religious ceremonies, not burial. The second phase of construction started around 2150 B.C. and involved installing 82 bluestones on site. These were huge stones, weighing up to 4 tons, that had to be brought in from the Preseli Mountains in Wales. The journey with these enormous stones was about 240 miles long.
Approximately 150 years later, the third stage of construction began. During this stage, more stones, called Sarsen stones, were brought in. Some of these stones weighed upwards of 55 tons and were arranged in the semicircle shape with which people today are most familiar.
The fourth and final phase took place around 1500 B.C. This stage involved rearranging the bluestones into their iconic horseshoe shape. There were roughly 60 stones originally, many of which are broken or missing today.