7,250 towering arcologies hold 100,000 people up to a mile into the sky with another 900,000 living in the underground hive.
One in Ten live above ground. For the rest, life isn't that good. It's difficult to navigate the labyrinthine design, and almost impossible to avoid the rampant crime. Now add in the corruption and violent cults, then to top it all off, your air, food and water quality varies wildly (and may contain up to 12% processed malcontents, debtors, and retirees). Also, there is no natural light source and you're forced to work by a brutal enforcer. Underground it's mainly a population of indoctrinated psychopaths, people who have never experienced sunlight (or even starlight), subsisted on a partial diet of fellow hive dwellers and who's only connection to anything outside is droning propaganda broadcasts that bellow throughout the hives cramped corridors.
Underground Transportation Tunnels connect to other Hive Towers.
So what's the plot? What happens?
Anything you want, it's 2139! These are just some ideas I thought were weird, like all the others I torture the players with.
When the recon team leaves the bolthole is there a hive tower looming in the distance, or is there a giant farm-bot tending circles of crops as far as the eye can see, or is there a colony of big ass rabbits quietly grazing nearby?
When I ran two sessions using this reality the recon team woke up lost in the middle of an ocean and used a life raft and drifted until a storm dumped them out and washed them ashore on the coast of Florida. They wandered the wilderness trying to survive, and met their end trying to fight off a pair of gastornis (terror birds) with their recently made spears. So technically I can use this setting again since it went basically unexplored.