The Gulf of  Mohiban around the city of Carnac, is famous for its many megalithic remains. There are fields of menhirs (Alignement du Menec, Alignement du Kermario en de Kerlescan) resembling modern war cemeteries. And there are also many menhirs standing alone. The biggest menhir, the Grand Menhir of Locmariaquer, lays broken on the ground and which weighs about 350 tons. There are about 3000 menhirs in the area, though there must have been many more in the very past.

On the little (private) island Er Lannic there is a stone circle which is very remarkable. Half of that circle is submerged which proofs that these megaliths are at least 7000 years old since in 5000 BC the sea level was a few meters higher lower than today.