The volcanoes that erupted thousands of years ago in what today is La Garrotxa region gave rise to great lava flows that occupied the bottoms of the local river valleys.
Over time, this volcanic rock has been sculpted and eroded by water, cold and heat into a spectacular line of cliffs and other singular geological sites. Sant Joan les Fonts and Castellfollit de la Roca are the municipalities with the most spectacular and well known lava flows, but there are others in some municipalities of the volcanic region of Olot.
