Arroyo Tapiado is a nice drive up a beautiful mudstone canyon within the Anza-Borrego Desert State Park. Outside of the fantastic views, Arroyo Tapiado has the highest density and the longest mud caves in the world, making it a unique place on Earth. It is no wonder why many people flock to see this natural wonder year around. One of the mud caves is over 1,000 feet long, which makes these mud caves seem to last forever once inside. With over 22 known mud caves, this area could provide a weekend of exploring. Just be warned, the mud caves are unstable and susceptible to collapse at any time. The dirt is very soft and will quickly collapse if touched. The park recommends not entering the mud caves.