Twice a year, in spring and autumn, the sun shines through a hole in a mountain ridge and lights up the church tower of Elm, a village in the Sernf valley of canton Glarus. The hole is the Martinsloch, a natural window in the Tschingelhörner, and it sits right on one of the most famous geological features in the world: a sharp line along the cliffs, clearly visible from the valley, where older rock lies on top of much younger rock. This is the Glarus thrust, and it helped geologists understand how mountains are built by the stacking of enormous slabs of the earth's crust. The Swiss Tectonic Arena Sardona was listed by UNESCO in 2008.
The arena covers a high, rugged area between the Linth, Rhine and Seez valleys, with peaks rising to over three thousand metres around the Piz Sardona, and glaciers, high pastures and deep valleys. Hiking trails lead to viewpoints where the thrust line can be seen up close, and information points explain the geology. On the Graubünden side, Flims and Laax are known for their skiing, and the Segnes plateau above Flims offers a superb view of the Tschingelhörner and the Martinsloch.
Nearby, the Rhine gorge, the Ruinaulta, was carved through the debris of the Flims landslide, the largest known landslide in the Alps, which fell some ten thousand years ago and buried the valley under billions of cubic metres of rock. The road from Flims toward Ilanz runs above the gorge, with viewpoints looking down onto the white cliffs and the river below.
For riders, the area offers a mix of great roads. The Oberalp road runs west from Chur past Flims and Laax and up the Surselva valley to the Oberalp pass and Andermatt, a long, fast route with lovely views. On the Glarus side, the road up the Sernf valley to Elm is a narrow dead end, but scenic, and the Klausen pass, connecting Glarus with Uri, is one of the classic alpine passes, with a twisting climb and spectacular views. The Klausen is closed in winter.
Domat/Ems, about eighteen kilometres away, and Chur have fuel and services; Flims and Laax have stations as well, and the villages of the Glarus valleys have more limited facilities. Try a Glarner Pastete, a pastry filled with almonds and plums, or Glarner Schabziger, a pungent herb cheese made in the canton for centuries, and look up at the mountains as you eat, imagining the slow collision that built them.