The word "megalith" means - literally - simply a rock of gigantic size.
The megaliths refer to - in the archaeological sense - the monuments built by our distant ancestors, between the 5th and the 1st millennium BC, and which are, or a part of them, still there.
In Armorican Brittany, megalithic constructions are particularly numerous and sometimes well preserved. Most are now protected, valued, and accessible to the public.
It could be :
cairns: construction of several tens of meters in length, in stone, covering a "gallery grave" that could serve as a burial place or place of worship. The most famous example, visible near Pleumeur-Bodou, is the famous Cairn of Barnenez.
Gallery grave: when a cairn has been dismantled over the centuries, it often remains only the skeleton of the internal passage, forming a "gallery grave", and sometimes even the last vestige consisting of some stones forming a "dolmen". There are many examples in Pleumeur-Bodou: the gallery grave of the Île-Grande, the gallery grave of Prajou Menhir (now part of the municipality of Trébeurden, left before the bridge of the Île-Grande), the gallery grave of Kerguntuil (now part of the municipality of Trégastel), the dolmen of Keryvon (at the edge of the road between Landrellec and the Île-Grande).
menhirs: the "standing stones", which Breton name is "peulvan", remain a mystery for archaeologists, but their ostentatious character suggests that they "signaled" a presence, that of a community or its necropolis. In Pleumeur-Bodou, the most famous example is the menhir of Saint-Uzec (also called "Penvern"), more than 6m high, and which had been "Christianized" during the sixteenth century.
Later, at the end of the pre-Christian era (Celtic and Gallic era), the menhirs evolved towards smaller and less crude forms, much more refined and stylized: the Gallic "steles" were often destroyed, or debited but there are still some of them in Pleumeur-Bodou, often on private land. An octagonal stele has recently been reported near the chapel of Saint-Uzec. And the most beautiful stele of all Brittany is none other than the famous stele of Trégastel, formerly visible at the Tourist Office of Trégastel.