The roof of Brittany, the Arrée Mountains, reach 385 metres a.s.l. at the roc’h Ruz, their highest point. They are characterized by the presence of rocky outcrops, the roc’h, and by rounded summits, the menez or tuchenn, combined with short grass moorland and peat bog landscapes, and a bocage network, the densest of Brittany. The “wild” feeling atmosphere is generated by the harsh pedological climate conditions.

The Atlantic moorland with heaters and gorses is characteristic of these landscape and hosts a flora of recognized European interest. With a high cloud covering and rainfall, this is the realm of the acid peats and humid meadows, which are poor in nutriments. The most remarkable are found north of the roc’h of the Arrée Mountains and in the swamps of Yeun Elez, which are home to one of the few highmoor bogs of Brittany, and to a raised bog unique in France.

This area is also home to renowned native forests of broad-leaved trees. For example, the Huelgoat forest, which has been frequented by visitors eager for romanticism since the 19th century, owes its fame to its well-known granitic boulder field and to a magical atmosphere which is sanctuary of Breton Celtic legends.
Old slate quarries are emblematic of this inner Brittany. The slate is a strong component of local built heritage, which remembers a mountainous way of building with squat and grouped housing.