Thank you, Clancy. This book is nothing like what I originally story-boarded, and in a way I'm happy about that. Evoking memories for a reader, especially a happy one is a nice compliment. When Trevor and Cassidy visit the Subway Cave near Burney, they shut off their flashlights to experience that total darkness. The side chamber that's mentioned has a interpretative marker indicating no external light can reach that spot. From what I've read, many of the tubes in Lava Beds are the same way. Shasta Caverns are beautiful and the way they light the formations is stunning. Sadly, and likely for safety reasons, they don't turn off the lights during the tour. I guess if it hasn't become evident from my writing, I find caves fascinating.