Mercer Caverns, about a mile north of Murphys in California, was discovered around 1885 by gold prospector Walter J. Mercer, who named the caverns and filed a claim on them. Formed in a marble unit of the Calaveras Formation, the cave is known for its dense array of underground decorations, including speleothems, stalactites, stalagmites, and a notable display of aragonite frostwork. A standard traverse tour descends 160 feet by 208 steps and exits by 232 steps between natural and artificial entrances. Mapped in 1986 at 3,389 feet long and 192 feet deep, it remains a developed cave valued for its geology and formations.