Cairn de Gavrinis

One of the most special neolithic ruins along the Morbihan coast, this giant cairn is out on the island of the same name. Dating from 4000 BC and measuring more than 50m in diameter, the beautifully situated tomb is well known for its profusion of intricate engravings. You access the site on a 15-minute boat trip from the harbour at Larmor-Baden (14km southeast of Auray), and it's important to reserve tickets in advance.