By around 2,500 BC, larger stones had been brought to the site, including giant sarsen stones from North Wiltshire, which could weigh as much as 30 tons.
Although they are smaller than the massive sarsens, the bluestones still weigh an average of 4 tons each, and archaeologists are baffled as to how they were transported so far without modern technology—or even the wheel!
At this point, sandstone slabs – known as 'sarsens' – were arranged into an outer crescent or ring; some were assembled into the iconic three-pieced structures called trilithons that stand tall in the centre of Stonehenge.