It's not the hugest cave, but it was large enough to take a couple of hours to tour. For Alice, that's usually more than enough exertion at a time. She did great, although she was going pretty slow towards the end.
The caverns were once outlaw hideouts and even a speakeasy during Prohibition. The CCC cleared it out during the Depression and built the nifty buildings above ground as well. There are some enormous deposits of calcite (lime crystals) down there.