Photo Gallery: Dangerous Openings
Dangerous Openings include shafts (vertical), adits (horizontal), and inclines (diagonal). They are dangerous because you cannot see inside of them, there is no depth perception, and you are exposed to gases, lack of oxygen, and critters. You may also encounter falling rock and decayed support beams and frameworks.
Shafts (Vertical openings)

Adits (Horizontal openings)
Inclines