Arcologies and vertical cities suggest concentrating population in tiny footprints. Maximum efficiency, minimum space. Mathematically, they make sense. Practically, it may make more sense to take those tall buildings and lay them on their side. Elevators that rise a mile into the sky aren’t as easy as a sidewalk or train running a mile. Buildings a mile tall must withstand the swaying from winds and quakes. Keep it short and keep it simple. Growing a mile-tall building means building another building. Growing a mile-long building means extruding another section. A city on its side may not minimize space, but it dramatically increases practicality. Besides, it’s easier to go for a walk outside if you don’t have to include a mile-long drop.
“Instead Of Vertical Cities, Should We Be Thinking About Linear Cities?” – TreeHugger
Pretending Not To Panic 