Inner circle: "The earliest portion of the complex dates to approximately 2950-2900 BCE (Middle Neolithic). It is comprised a circular bank, ditch, and counterscarp bank of about 330 feet (100 metres) in diameter. Just inside the earth bank is a circle of the 56 Aubrey holes that held wooden posts."
Sarsen circle: "The Sarsen Circle, about 108 feet (33 metres) in diameter, was originally comprised of 30 neatly trimmed upright sandstone blocks of which only 17 are now standing. The stones are evenly spaced approximately 1.0 to 1.4 metres apart, and stand on average 13 feet (4 metres) above the ground. They are about 6.5 feet (2 metres) wide and 3 feet (1 metre) thick and taper towards the top. They originally supported sarsen lintels forming a continuous circle around the top. Each lintel block has been shaped to the curve of the circle. The average length of the rectangular lintels is 3.2 metres (10' 6"). The lintels were fitted end-to end using tongue-and-groove joints, and fitted on top of the standing sarsen with mortice and tenon joints. The Sarsen Circle with its lintels is perhaps the most remarkable feature of Stonehenge in terms of design, precision stonework, and engineering."