So I am really stuck on this, and I posted something similar in the 3.5 forum but got responses I didn't like. Most of them used 3.5 mechanics... I want to do something completely different.

So here is the back story, party all at this opera house which is in a city built on top of a city (kinda like in futurama), and a explosion goes off in the opera house. I want the entire first session to be a survive challenge for the group to survive the fall and the collapse of the city above them.

What are some cool ways to do this? Maybe use board game mechanics or just some interesting cinematic scenarios you'd recommend. If you say anything related to skill checks I will scream (not that you would hear me). Talk to me, I am gonna go watch some Indiana Jones movies for some inspiration. I want this whole thing to be about creativity, pressure, and drama.

What I have so far:
A chasm the party must cross, but only one at a time and it keeps getting larger. The party must decide under time restrictions what the order will be. Mind you there are several NPC's as well.