Discovered in 1885 by prospector Walter Mercer, these limestone caverns are a genuine surprise — a series of chambers decorated with aragonite crystals, stalactites, and cave formations that took millions of years to grow. The geology here is unusually varied: different chambers hold different formations, and one room contains helictites growing in defiance of gravity. Guided tours run regularly and last about an hour. The caverns stay a cool 55°F year-round, so bring a layer regardless of the season.
Mercer Caverns
1885 limestone caverns with aragonite crystals and stalactites
A story
Walter Mercer stumbled onto the cave entrance in September 1885 while prospecting for gold on the hillside north of Murphys. He lowered himself in with a candle and found not ore but something rarer: an intact series of chambers coated in aragonite crystals and Gothic-arch stalactites. He opened the caverns to paying visitors within a year, making Mercer Caverns one of California's earliest commercial caves.