The huge stone mass making up the Petit-Mont cairn (still more than 10,000 m3 today) was formed over a long period. It results from an "accretion" process found on many great megalithic sites.
However in Morbihan, it is the most impressive case to date. It was built in three main stages.
The three interconnected cairns of Petit-Mont : a typical case of megalithic "accretion"