Spelunking is very different from simply walking through a spacious cavern. My experience involved crawling on hands and knees through underground tunnels, and I describe it in this article.
My Spelunking Experience: Crawling Through Underground Caves
Spelunking in the California foothills. Information and directions.
4 Caves Worth Exploring Here in California
Peppersauce Cave in southern Arizona is relatively well known but not a tourist attraction. It's in a wilderness area on the north side of Mt. Lemon in the Santa Catalina mountains north of Tucson.
Exploring Arizona's Peppersauce Cave in the Coronado National Forest
Crystal clear waters, rugged caves and underwater caverns are just a taste of what Bruce Peninsula National park has to offer.
Cyprus Lake and The Grotto - Bruce Peninsula National Park