On the island is a prehistoric site, an allée couverte (gallery grave), known as Ty Liac'h, built in the Neolithic period.
It is in the central part of the ridge of the island.
There are ten upright stones, supporting three horizontal slabs.
There are other stones on the ground which once were supporting stones; there was at least one other horizontal slab.
The original length was 14–19 metres (46–62 ft), and it had a lateral entrance on the north side.

It is south of an adjacent field in which, from aerial photographs, traces have been detected of about twenty prehistoric circular huts.
On the island is a prehistoric site, an allée couverte (gallery grave), known as Ty Liac'h, built in the Neolithic period. It is in the central part of the ridge of the island. There are ten upright stones, supporting three horizontal slabs. There are other stones on the ground which once were supporting stones; there was at least one other horizontal slab. The original length was 14–19 metres (46–62 ft), and it had a lateral entrance on the north side.
It is south of an adjacent field in which, from aerial photographs, traces have been detected of about twenty prehistoric circular huts.
Île Milliau