The forest road is crossed by a narrow strip of dark red rocks that stand out from the grey and brown ones. They derive from the ancient sands of a desert environment and were formed about 260 million years ago, at the end of the Palaeozoic, during the Upper Permian. They are called  the Val Gardena Sandstones and are widespread further west, near the Rio Cordin. Their peculiarity is that here they have been set among older rocks by the tectonic upheavals that generated the Alps.