At the boundary of the bishoprics of Cornouaille and Léon the landscape is similar to that of Ireland and Wales. The typical Argoat, or inland Brittany countryside is comprised of rocks with mainly moorland flora. The name of this area is Monts d'Arrée and its origins go back to the Primary Era, or Paleozoic, 300 million years ago.
At that time, Monts d'Arrée consisted of mountains 2,000 and 3,000 metres high. Continuous erosion over the centuries subsequently lowered their altitude by an average of 100 to 200 meters. Roc' h Ruz, the highest of the Monts d'Arrée peaks, is now 385 metres above sea level. The Monts d'Arrée landscape, with its moors and rocks, but also with charming chapels and churchyards, can be explored on foot or on a mountain bike.