The Rhine gorge — the Ruinaulta in Romansh — lies in the valley below Breil/Brigels, and trails from the village descend into it. The gorge was carved over thousands of years by the young Rhine cutting through a massive rockfall, creating sheer limestone walls, turquoise water, and a dramatically narrow canyon. It has been called the "Swiss Grand Canyon," which overstates it, but the scenery is genuinely striking.
The most accessible walk follows the valley floor through the gorge between Ilanz and Reichenau, a section of about 15 km. From Breil/Brigels, you can descend to Tavanasa and join this walk, then return by train on the Rhaetian Railway, which runs along the valley. The train journey through the gorge is itself one of the most scenic stretches of rail in Switzerland.