For the past 90 years, archaeologists have been scouring Pembrokeshire's Preseli Hills in search of clues that could shed light on where the bluestones used to build the famous monument came from. But it turns out that the rocks may have originated from another hill — one that's just a mile away.
Just where the massive rocks came from, and how they were transported from so far away, is a mystery that still baffles archaeologists. Back in 1923, geologist Herbert Henry Thomas proposed that the distinctive spotted dolerites were hauled from Wales to Wiltshire some 5,000 years ago via land and sea — a distance of 150 miles (240 km). A more recent theory suggests they were carried east on an ice-age glacier about 20,000 years ago.