Er Lannic cromlech, Neolithic cromlech in Arzon, France

Er Lannic is a Neolithic stone circle in Arzon with two horseshoe-shaped arrangements of standing stones set on gently sloping ground beside the water. The southern circle now sits partially submerged, making the ancient site accessible only by boat.

The site was built about 6000 years ago during the Neolithic when early communities erected stones for ritual or social gatherings. Excavations in the 1920s revealed tools, pottery, and dwelling remains that show people lived here over an extended period.

The stones bear carvings of axes and cup marks that reveal how Neolithic people in Brittany expressed themselves through art and demonstrated their technical skill.

The site is visible only from the water and is best visited by boat from Arzon. Guided tours often combine this visit with the nearby Gavrinis cairn to create a more complete outing.

The two enclosures differ in build: the southern circle's stones are larger, wider and more evenly spaced than those of the northern one, which may mean they were raised in two separate periods. At the junction stand three larger slabs and a broken menhir 8.20 m long.