3 Best Sights in Sacramento and the Gold Country, California

For different sorts of underground jewels, wander into an ancient limestone cave, where stalactites and stalagmites, not gold and silver, await. Take the 235-step Spiral Tour down a staircase built in 1922 into the vast main cavern, or descend farther on the Expedition Tour caving adventure. It's best to make a reservation here.

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.

Lighthearted, well-informed guides lead 45-minute tours (208 steps down, 232 steps up) into caverns a prospector named Walter J. Mercer discovered in 1885. Millions of years in the making, the sheer, draperylike formations and aragonite crystals that resemble snowflakes are enthralling. Dress in layers (even in summer) and wear nonskid closed-toe shoes for this mildly strenuous adventure.