The Butte de César (very visible 150 m from the road) is a tumulus 56 m in diameter and 18 m high.
This pile of stones, covered with a layer of silt and black earth, was explored in 1853.
On the southwestern part an open trench opened leading, after a rudiment of covered alley, to a central chamber.
This is made up of three monolithic supports covered with a large slab of quartz.
The alley itself, now partly collapsed and filled with silt, was covered with two slabs resting on masonry walls.
In the room and the aisle were found many megalithic objects and tools (jasper necklaces, axes, pottery ... today exhibited at the Museum of Prehistory in Vannes).
Classified in 1926, the Tumulus was the subject of new excavations and works in 1934, which brought to light several secondary burials.
The tumulus is a witness of the important pastoral and agricultural tribes which then populated the tour of the Gulf of Morbihan.
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