Preseli spotted dolerite was mined in the Welsh Mountains 200 miles away
Archaeologists have discovered a mini-Stonehenge, a mile from the site of Wiltshire's famous stone circle.
"Bluehenge", named after the hue of the 27 stones from Wales which once formed it, has been described by researchers as a "very important" find.
All that now exists of the 5,000-year-old site is a series of holes where the dolerite monoliths once stood.
Bluehenge lies at the end of the "Avenue" - a pathway connecting the larger Stonehenge to the River Avon.
The remains of the monument was unearthed over the summer by researchers from Sheffield University.
It is thought it was erected around the same time as its neighbour Stonehenge.
The circle was made using the Preseli spotted dolerite stone.
It is a chemically altered igneous rock - harder than granite - which was mined in the Preseli Mountains in Pembrokeshire and dragged 200 miles to the site on the banks of the river.
Full details of the Bluehenge discovery will be published in February.
Stonehenge has been found to have a smaller neighbour
Archaeologists have revealed that evidence of a second stone circle has been found near the site of  in the United Kingdom. It is thought the smaller circle was built around the same time, making it 5,000 years old.

Only chips remain of the 27 stones that made up the site, which was built from  rocks thought to have originated in the  in Wales. From there they were dragged 200 miles to be built just one mile (two kilometres) from Stonehenge.

Because the rocks it is made from are known to appear blue, the site has been given the name . Although the stones are gone, the holes they left remain. Stonehenge was linked to the  by a pathway, and Bluehenge lies at the end of it. 

The BBC quotes researchers working on the site, which was excavated over the summer by , as calling the discovery "very important". A full report is expected in February 2010.