Fodor's Expert Review Black Chasm Cavern National Natural Landmark

Guided 45-minute tours take you past stalactites, stalagmites, and rare formations of delicate helictites in three underground chambers, one of which also contains a lake. Black Chasm isn't the largest cave in the Gold Country, but its crystals dazzle both eye and camera—the Landmark Chamber, the tour's third stop, inspired a scene in the 2003 film The Matrix Reloaded. Outside is an area where kids can "pan" for crystals.  The same outfit also conducts tours of California Cavern State Historic Landmark, 32 miles south of Volcano, though the days open are less regular.