I've been all over this level for 3 days on and off. I've consulted the walkthroughs at gamefaqs.com. I've pulled my hair out.
I'm in The Abyss. I've gotten all the way into the lava-filled area. I've gotten into the room with the three atomic healths and the babe up the lava stream. What I -haven't- found is a way to progress in the level. There are references to raising a staircase of stones, but I have yet to find the trigger that does this.
Anyone know where I need to be going based on this description?

I know where you are but I don't know exactly how to explain. So chek the video and probably you will find out: http://www.youtube.com/watch?v=FbaF-nDVQsw

Yeah I was trapped here too. The part where you have to go to after that is REEEALLY obscure, as you can see from the video

ah yes those stairs. Don't remind me.

You can also go here for the walkthrough (and also lists/shows where all the secrets are).
http://www.3drealms.com/duke3d/walkthrough/index.html

Obviously not just me, then. :)
I've watched the video to the point where I think it'll help me, and a bit past that. Should help. Thanks for the assistance, folks!

Sweet! Finished that level. Didn't remember from ye olden days that it was the end of the first act. Cool.
Thanks so much for the help on that. You're right, too...it's REALLY obscure, because one of those switches that raises the stairs must also create the holes in the canyon...or some trigger about being in that room does it. Because you don't have to go through that room to get to the canyon.
Very, -very- obscure. Ah well, past that and onwards!

Ha, I always just cheated on that level. It's way too long and difficult to belong in the first episode. I don't know what the devs were thinking. The obscure switches only make it worse. They should have made it a bonus level or something.

I think the 3rd level of the second episode is the real torture. I didn't experience any difficulty in the abyss.