I like to think of planes flying low through populated areas. It sounds dangerous and it would be noisy beyond belief, but I can't help thinking that it would be fun for both the pilot and the people on the ground. There must be a way to make this work.
On another subject, I'm guessing that under Earth mines will be dug artistically with a view toward what can be done with the tunnels when the ore's run out. Even empty mines will be valuable assets.
If you're a present day private pilot you no doubt avoid the inside of clouds. Pilots die all the time in clouds...you can't see what's ahead when you're in them. Accident avoidance technology will make all that a thing of the past.
Maybe only public transport will be allowed to do it.
Twisted structures are being discussed.