One day while in the Redding, CA area, we went on the Shasta Lake Caverns tour. It included a bus ride down to the lake, a boat ride across the lake, another bus ride up to the caverns, and the caverns themselves, which included at least 600 steps. These caverns were quite different from the ones in Montana (Lewis & Clark), and very interesting.
We had gone there the day before only to find out that it was closed for a special party. Not happy campers to have to drive back. But it was worth it.