You have fallen into a hole.
You find yourself in a small stone room. The only exit appears to be the hole which you fell through, now far above you in the ceiling. There is straw scattered on the cold, cobbled floor. The darkness of this cell seems to swallow up the thin shaft of light falling from above.
A voice from the shadows says "404".
However, before you scream in terror or allow a soul destroying malaise to settle upon you like the dust of ages (what? it already has?), let me help you out.
Oubliette Escape Route:
As you stand in the gloom your eyes adjust and you see three small wooden doors set in rough hewn walls. Each door has a small hand painted sign nailed to it:
You hear something shuffling around in the dark behind you. I'd recommend getting out of here quickly.