The Déroc waterfall is located at the end of a small path starting in the village of Nasbinals. A ravine runs alongside the Gambaïse stream, whose glacial valley is dominated by the cascade. Under the basalt ledge from which the waterfall flows, a cave has formed. Its ceiling is made of large basalt prisms with remarkable geometry, also called volcanic organs. They are shaped by the particular flow of basaltic lava due to some shrinkage cracks during its cooling.