The Croscat is the youngest volcano in the Iberian Peninsula — its last eruption took place around 11,500 years ago — and at 160 metres above the surrounding terrain it is also the tallest cone in the Garrotxa. For most of the 20th century its flank was being mined for grederas, the dark-red volcanic gravel used for paving and landscape gardens.
When mining stopped in the 1990s a vast vertical cross-section of the cone was left exposed, and rather than restore it the park decided to leave the cut as a geological exhibit. Walking up to the viewpoint, you look directly at the internal layering of an eruption — successive bands of scoria, ash, and bombs stacked one on top of the other, the rock textbook open at full size. The colour is extraordinary: the entire face is the rich brick-red of oxidised iron.