High Quality Volcanic Rock with cracks and dihedrals. Most of the routes have slings for rappelling or have chockstones that could be slung. Longer routes will require two ropes to rappel.
All the way up the Maipo Valley from Santiago (about two hours drive) to Banos Morales. One hour hike towards Volcan San Jose; on the approach, the columns will be obvious on the right side of the volcanoes flanks.