Earth Pyramids, a wonder of nature. The Renon Earth Pyramids are the highest and the most aesthetically pleasing in Europe. Earth pyramids are a phenomenon of erosion. They originate where ice-age glaciers have deposited moraine clay in valleys. When it is dry, it is rock-hard. If it comes into contact with water, it turns into a clayey pulp that flows down into the valley. However, when protected from the rain by large stones, the clay remains dry and hard. Only the part around the stone erodes. This is how earth columns are formed and become higher each time it rains. If the top stone falls off the peak, the column is certainly doomed to a quick decline because the clay is exposed to the rain and then carried away by it. The earth pyramids in the valley of the Rio Gasterer at Auna di Sotto have a special grey colour.