Dolmens, literally « stone tables » in old Breton, served the function of communal burial places for
waterfront communities. This tomb was doubtless used for centuries by numerous generations as a resting place for their dead.
The dolmen at Onnens, a prehistoric funeral monument, was uncovered in 2000. The discovery was made in the course of large-scale pre-emptive archaeological digs undertaken prior to the construction of the A5 motorway. During the dig at the place called « Praz Berthoud » archaeologists discovered an ensemble of five large blocks of stone.
The largest of these slabs measures more than 3.5 metres in length and weighs around six tonnes! Underneath they brought to light six large oval trenches. One of these contained some organic sediment in which were found bones and human teeth.
The monument is impressive. In 2010 it was put back in place a few metres away from its original site, along with the slabs found on site and three new slabs carved from granite from the Tarn. Additional information is to be found on the display boards at the site.