You're a DM. You make a dungeon. You keep a version of the dungeon maps and key on something like Google Docs. After your run your players through this dungeon you make notes in the Google Docs files regarding what monsters have been slain, what treasures have been looted, where the bodies of dead PCs lay, and other state changes in the dungeon. Probably by using "strikeout" text and colored text and the like. Maybe you restock this dungeon, maybe you don't.

Than you pass along these files to another DM that you know through the internet and they run their players through this dungeon. Maybe they restock the dungeon beforehand, maybe you have already, maybe it doesn't need restocking.

After they run their group through this dungeon they make their notes regarding changes, etc. I'm sure there's some collaborative editing features for online documents that makes this viable while also maintaining a history of the changes and who did them and when.

And they pass the dungeon back to you for when you next run your players through it, or maybe they pass it along to another DM and the cycle continues.

Maybe along the line these other DMs add new levels and the like to the dungeon, further mutating it.

It would be hard to get this to work properly, but it'd be a lot of fun if it did. Often sending an adventuring party through a dungeon causes a massive amount of carnage and some interesting changes and it makes the dungeon feel more "real" than if the PCs always seem to be the first adventurers in an area.

Logistically, rather than passing around a single dungeon, it'd probably get easier to set up a database of a few different dungeons with notes on different iterations due to having been hit by different groups.