Postcard entitled: "Sun worship Carnac Alignment, France". The Carnac stones are an exceptionally dense collection of megalithic sites around the French village of Carnac, in Brittany, consisting of alignments (a linear arrangement of upright, parallel megalithic standing stones set at intervals along a common axis or series of axes), dolmens (single-chamber megalithic tomb), tumuli (mound of earth and stones raised over a grave or graves) and single menhirs (a large upright standing stone). More than 3,000 prehistoric standing stones were hewn from local rock and erected by the pre-Celtic people of Brittany, and are the largest such collection in the world. The stones were erected at some stage during the Neolithic period, probably around 3300 BC, but some may date to as old as 4500 BC. In 1887, H. de Cleuziou argued for a connection between the rows of stones and the directions of sunsets at the solstices. There are also theories on the use of the stones as astronomical observatories, as has been claimed for Stonehenge.