Experts believe ancient Britons prized the Salisbury Plain as a convenient hunting ground. In addition, a natural causeway created by glacial heaving and thawing formed a grooved "avenue" that coincided with the rising of the summer solstice sun as it leads up to the current Stonehenge site. While today we understand this as a natural coincidence, these ancient peoples could have considered it a sacred place divinely designed.
During the first phase of building Stonehenge, in approximately 3000 B.C.E., ancient Britons used deer antlers to dig a ditch along the perimeter of a circular enclosure about330 feet (100 meters)across, with a high bank on the inside of the circle and a low bank on the outside [source: Pearson]. The "henge" in Stonehenge refers to this earthen enclosure that was unique to ancient Britain. We know of about 50 certain henges in existence [source: Last]. However, the ditch that encloses Stonehenge isn't a true henge. Instead, it's backward; a true henge has a ditch on the inside of a bank [source: Pearson].
The designers left one wider entrance on the circle's northeast end, leading toward the avenue, and one narrower entrance on the south side. In the 17th century, antiquarian John Aubrey identified 56 holes along the inside perimeter of the circle [source: Pearson]. These "Aubrey Holes" could've held wood posts or perhaps bluestones. Other archaeologists have discovered cremated human remains in and around these holes — likely placed there over the next several centuries after the trench was dug. Archaeologists have also discovered numerous other postholes inside the ditch, suggesting perhaps that wooden structures stood there or that the posts themselves mapped astronomical movements. Archaeologists believe the Britons could have erected the Heel Stone during this first phase or perhaps earlier.
The next stage of Stonehenge's development occurred between 2620 and 2480 B.C.E., when the ancient Britons erected the sarsen horseshoe and outer circle [source: Pearson]. They meticulously shaped the sarsen stones to fit the desired design of the monument, with tapered upright sarsens and a remarkably level surface along the top of the lintels in the outer sarsen circle.
Around 2300 B.C.E., the ancient Britons also dug ditches and banks along the borders of the avenue leading to Stonehenge [source: Pearson]. The avenue was about 40 feet (12 meters) wide and 1.7 miles (2.8 kilometers) long and followed an indirect route to the River Avon [source: Pearson]. Over the next several centuries, the bluestones were repositioned to where they are now, presumably to fit new purposes of a changing society.