Locmariaquer, The Er-Grah tumulus is 140 metres (460 ft) long. The Locmariaquer megaliths are a complex of Neolithic constructions in Locmariaquer, Brittany. They comprise the elaborate Er-Grah tumulus passage grave, a dolmen known as the "Table des Marchand" (Merchant's Table) and "The Broken Menhir of Er Grah", the largest known single block of stone to have been transported and erected by Neolithic man.