Here you'll find everything from sea caves off the Channel Islands and La Jolla to ancient lava tubes of dorment volcanoes. California also has a few mines that offer underground tours to the public and some are active mines that welcome you to take your findings home. Whether you're a spelunker, treasure seeker or just interested in going underground, California has something to suit your interest. Most caves and mines hover around 60 degrees year round, making these underground attractions a great place to cool off on a warm summer day.