Named after the discoverer of the caves, Walter J. Mercer, the caves came into the public eye in the year 1885. Naturally formed in a Calaveras formation, these caves boast of housing a huge collection of speleothems, stalactites and stalagmites. A unique natural phenomenon can also be spotted here, which is Aragonite frostwork. Artificial entrances have been made for the caves to be easily accessible by people, although, natural entrances are also available. A unique activity to undertake while you are on tour, have a great time here.

• Rented cars