Les megalithes du departement du Morbihan aims at a better understanding of megalithism, or more precisely megalithisms, and presents a new approach to the relationship between standing stones (menhirs) and tombs (dolmens). The architectural analyses developed raise questions about their complementarity. They are based on a corpus of architectural plans comprising 1413 megalithic monuments from the Department of Morbihan, including 13,200 vertical slabs, the result of thirty years of research and field observations, and including more than 250 unpublished monuments. Two main approaches are discussed: descriptive architectural analysis of the plans on the one hand, and analysis of landscape and environmental elements on the other. The parallels between the stones erected in the open air and those, sometimes identical in their dimensions, their morphology and their geology, which constitute the rooms, the corridors, and the facings of the funerary monuments, consolidate and develop observations already made by other archaeologists on the reuse of these Neolithic standing stones. The observation that these parallels extend to the symmetry and aestheticism of the structures is quite new. These unprecedented and convincing results brought by this analysis of the alignments of standing stones and funerary architectures demonstrate how a subject that has been explored since the nineteenth century by many researchers can still reveal hidden truths.