Lava tubes
“Tabernacle Lava Tubes.” The Dye Clan, July 20, 2013. Wikimedia Commons (CC BY-SA 3.0). https://commons.wikimedia.org/wiki/File:Tabernacle_Hill_Lava_Tubes,_DyeClan.com_-_panoramio_(8).jpg.
“Tabernacle Lava Tubes.” The Dye Clan, July 20, 2013. Wikimedia Commons (CC BY-SA 3.0). https://commons.wikimedia.org/wiki/File:Tabernacle_Hill_Lava_Tubes,_DyeClan.com_-_panoramio_(8).jpg.