I think I'm gonna name my firstborn son "Cities: Skylines modding community". I pretty much have to, at this point.
Steam user Ulysius has released a mod called "Flight Cimulator", a riff on Microsoft's classic Flight Simulator series. It lets you hop in the cockpit and fly planes over your city because what genre even is this anymore? Is it a city builder ala SimCity, or are modders constructing a cotton-candy-strewn rainbow road to our wildest dreams, The One True Video Game?
Excitement aside, the mod is pretty new, so there's still work to be done. Foremost, Ulysius wants to add collisions, though whether they will cause structural damage to buildings or not is still, ahem, up in the air.
Still, you can go fly a plane around a city that you crafted with your own hands and the more architecturally inclined folds of your brain. That's pretty rad. Oh, and if that's not enough (or you're just getting started with Cities: Skylines), try some of these other excellent mods.