When the old-fashioned skyscrapers were no longer adequate to serve the civilization's needs, we built flexible organic structures on top of them. Why go miles down to street level? Just grow bridges between buildings with fast-maturing biological materials.
These images of a futuristic city built in layers are by French concept designer François Baranger, who has worked on everything from videogames to Harry Potter movies. These images are early concept art from a Luc Besson film called Ektor that got canceled before shooting began. I wish we could have seen what Besson, director of The Fifth Element and the forthcoming Extraordinary Adventures of Adele Blanc-Sec, would have done with these images. Looks like a smashing good time.