If you want to see stuff like the russian napalm fort, check out the lava tubes on Maui. Or probably any lava tubes. Everything looks like it's been covered in melted chocolate, then flash frozen Ok, not everything, but a good portion of the tube.
Here is a shot of a lava tube on the big island. Creepy down there. I had just watched that movie Descent about a week before the trip....and that didn't help.