Here's a pic from Hawaii Volcanoes National Park. This is the departure end of the Thurston Lava Tube. This first section is about 100 meters long and is lighted. There is a second section that starts at the gate Carol is standing at that is unlighted and 383 meters long. Couldn't get her to go exploring for some reason. I mean it's not like I didn't have a flashlight... And the gallery is here.