The Ruinaulta — the Romansh name for the Rhine Gorge — is one of Switzerland's great geological spectacles: a 14-kilometre canyon carved through ancient landslide debris, with white limestone cliffs rising up to 350 metres above the turquoise Vorderrhein. You can see it from the train (the Rhaetian Railway threads through it, offering dramatic views), hike along the valley floor, or tackle it on a raft.
The gorge holds UNESCO World Heritage status as part of the Swiss Tectonic Arena Sardona, recognised for its geological importance. The viewpoint at Il Spir, a cantilevered platform on the rim above Flims, looks directly down into the canyon. On foot, the most rewarding route follows the river through the gorge from Versam-Safien station to Reichenau, about three hours of walking through forest and rock on mostly flat trail.