Photo: Stephen Alvarez / National Geographic
NatGeo photographer Stephen Alvarez took this amazing shot of the Stephens Gap Cave in Alabama. As you can see, you'd need to rapel down the sunlit entrance to the left, or simply walk down the dark entrace to the right.
Mark Jenkins of National Geographic went spelunking for this fascinating article:
I'm about to back out when my shovel breaks through. I feverishly round out the hole and cram my head through. There is a low, triangle-shaped crawlway ahead of me. Surging with adrenaline, I try dragging myself into this new passage, but my chest gets stuck.
From the beginning I have been hyperfocused on digging in order to stave off dark, horrifying feelings of claustrophobia. But now, stuck like a rat in the throat of a snake, a sickly anxiousness sweeps over me. I violently kick my legs, but to no avail: I'm swimming in dirt. I realize that by not using the drag tray to remove the dirt, I've buried myself.
I try to calm my racing thoughts, but my mind is preoccupied with the millions of tons of rock above me. I've been told that caves seldom collapse, and yet here I am, trapped at the bottom of a breakdown, in a cave that obviously did collapse. I try to slow my frantic breathing because I've also been told that hyperventilating expands one's lungs and only tightens the squeeze, which is exactly what's happening. Suddenly I'm thrashing shamelessly, kicking and clawing and writhing. I manage to knock off my headlamp, and everything goes black.