Carlsbad Caverns National Park
You are in a deep and dark cave.
You have descended a narrow, winding path as it zig-zag's into the Earth's open maw. The last light of day is but a memory, a faint glimmer far above and behind you. In a few more turns you're sure even that will be lost. From ever so far below a soft eldritch glow rises ...invitingly? ...menacingly? Regardless, you boldly place one foot in front of the other and continue dropping into this alien realm.
Welcome to Carlsbad Caverns.