How would you guys handle mapping a 'dungeon' that is actually just several layers of buildings that have collapsed overtop and around each other? I'm building a ruined city that is currently being explored but the last thing they'll be doing is travel through layers of collapsed buildings to get underneath the city to the BBEG boss fight. It's probably going to be my biggest dungeon yet and I want to make it awesome but I'm struggling with how to go about it.

If you want to imagine a sort of fantasy New York city with lots of sky scrapers that have been without maintenance for 1000 years and are falling to time, that's kind of what I'm going for. Perhaps lots of jumping between buildings, collapsing ceilings/floors, things like that.

If you know of a map that matches that vibe, even better, I'm a visual learner and would probably do better with an example but my internet searches haven't produced anything yet. I know it's something used in video games a lot but none of the maps I'm finding are quite right. Thanks for your help!