The carved passage

The passage is 14 metres long and about 1.3 metres wide, lined with 29 orthostats (upright stone slabs) on both sides and covered by capstones overhead. Twenty-three of these slabs are decorated almost entirely in dense, layered abstract engraving covering the stone surface from floor to ceiling: spirals, concentric semicircles, sinuous lines, chevrons, U-shapes, axe motifs, and curvilinear forms fill every available surface. The visual effect is overwhelming — an interior seemingly alive with pattern, as if the builders intended the passage to function as an immersive symbolic environment rather than merely a corridor.

The carvings are not representational: there are no animals, no human figures, no narrative scenes. The system of signs appears to be symbolic rather than pictographic, possibly encoding cosmological, genealogical, or ritual information, but no consensus interpretation has emerged. Some researchers have identified recurring motifs — particularly the wavy line interpreted as a serpent or the shield shape — that recur at other Morbihan sites, suggesting a shared symbolic vocabulary across the megalithic communities of western Brittany.

The burial chamber at the end of the passage, roughly rectangular and roofed with a single large slab, is the part of the monument that originally contained human remains and offerings. By the time of modern excavation it had been largely cleared, but traces of cremated bone and pottery fragments were recovered.