That video is striking. Did you ever read the NYT bestseller, "23 Minutes in Hell" by Bill Wiese? In it he talks about a vertical tunnel he fell through that is about 35 feet wide and is apparently the gateway to hell. The width of the vertical in that video looks pretty accurate.
Found it scouring the web looking for some appropriate branding for the YBPDLN Ping List.
Never read it. Might have to.
What does YBPDLN mean?