Moaning Cavern is the largest single cavern cave in California or the West Coast for that matter, limestone and over 400 feet deep, tour guides say large enough to fit the Statue of Liberty inside. Our family has been visiting it for few years. Other humans obviously much longer as the oldest human remains, skeletons, in North America were found at the bottom.
Most certainly one of the coolest things to see in the California former Gold Rush area just a few miles outside Angels Camp. Total 5 stars and a must see. Awesome fun and friendly staff that love the cave and showing it to you. You should set aside at least a few hours or make it a whole day.
A giant pine cone!
...as others have mentioned it's a hot spot to rappel down, . We used the 280+ steps some odd creaky, really scary spiral staircase down to the bottom, as -always-. You can keep your ropes.
On the road again....