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About 18 miles (30km) west of Rennes, the forest of Paimpont is all that remains of the vast woodland that covered ancient inland Brittany (aka Argoat). Legend has it that the 25 square miles (40km2) of woodland is also the location of mythical Brocéliande, the forest of King Arthur.  
The 'Pierres Droites' are the alignments of menhirs at Monteneuf, to the south of the forest. The site has been excavated seven times and around 40 of the stones have been raised to their original vertical position
The first attestation of the site was made by Canon J. Mahé in 1825, citing the presence of "7 to 8 Peuvlans (Menhirs) in the area". Until fires ravaged the moors in 1976, the site was almost forgotten as the main part of the site consisted of stones lying completely or partially covered with heathland vegetation. 
The stone circles in the British Isles and Brittany are a megalithic tradition of monuments consisting of standing stones arranged in rings. These were constructed from 3300 to 900 BCE. It has been estimated that around 4,000 of these monuments were originally constructed in this part of north-western Europe during this period. Around 1,300 of them are recorded, the others having been destroyed.
Their original purpose is not fully known, but archaeological investigation has shed some light on it. It is widely thought that they served a ritual or ceremonial purpose, particularly in relation to solar and/or lunar alignments. In a minority of cases, some were also used as cemeteries, with burials being made in and around the circle.