They emerge from the forest like sharp teeth. The material comes from moraine clays deposited by erosion in the ice age creating these interesting pinnacles that are today a symbolic feature of the municipality of Renon.
When dry, this moraine clay is as hard as stone; when wet it is as soft as butter. The formation of the earth pyramids is possible only when there is a larger rock above them to protect them. Because the moraine contains larger rocks the probability of an earth pyramid being formed is very high. The formation and duration of a pyramid depends on various factors. If the protective larger rock falls, the pinnacle will melt quickly. The pyramids can be seen on the Renon in the Rio Fosco Valley between Longomoso and Monte di Mezzo, in the Katzenbachtal below Soprabolzano, in the Fosso di Castero near Auna di Sotto and near Gasserlahn at Auna di Sopra.