The Grotte di Stiffe (caves) are, technically speaking, a resurgence, that is, a point at which a river returns to the surface after a stretch underground. In the case of the Stiffe this point is located at the top of the gorge above the small village of the same name. The presence of this watercourse, that reaches large flows in some periods of the year, is certainly the most important feature of the Grotte or Caves, where there's sometimes a little stream that murmers and other times a fast flowing river running down the valley, creating rapids and waterfalls, with an deafening roar.