Cairn de Barnenez in Plouezoc'h

You're standing at the Cairn of Barnenez, on a peninsula on the north coast of Brittany. In front of you is a huge, stepped mound of stone. It's about seventy-two metres long, up to twenty-five metres wide and more than eight metres high. It almost looks like a natural slope, but every bit of it was piled up by hand. Turn around for a moment and look out over the Bay of Morlaix. When this was built, that was probably still a fertile coastal plain.