The Devil's Grotto is a narrow passage between massive boulders, descending steeply into a dark cavity along the river gorge. Getting in requires a short climb down on fixed ladders — it is not difficult, but the descent into the shadow of the rocks with a river rushing below gives it a proper sense of drama.
The name is explained by the setting: on a grey Breton day, the dark crevice, the sound of water underground, and the sheer scale of the surrounding boulders make the place feel genuinely otherworldly. Arthurian legend attached itself to this landscape for good reason.
The Grotte is part of the main walking circuit through the boulder chaos and is signposted from the village. The trail continues past several other formations, including the Champignon (a balanced rock), before looping back.