One thing I remember is that up to that big chamber they are talking about with all the various passages coming off, there were multiple strings of twine that went off in various directions from people using that to find their way back. That's as far as I ever went and only the one time because the squeeze to get there was not pleasant. I was 140 lbs back then and it was tight as fuck for me. You had to go through with your arms in front of you and inch worm your way for at least 10 feet and it seemed like a mile. Your clothes would hang on stuff and sometimes you'd feel like you were stuck and would have to shift your position to angle your shoulders right. I'm in a cold sweat just remembering it 40 years later. We had those cheap ass flashlights too that would just randomly dim out and you had to shake them. In retrospect, like many of the things we did when young, it was pretty damned stupid based on our level of preparedness. No foot, no water, one extra set of batteries, no helmets. Dumb, dumb, dumb.