Minecraft wiki entry for Building_a_metropolis, associated text: Skyscraper Build an incredibly tall building out of stone or stone-related blocks (or some similar blocks) and have lots of windows. You can add a piston elevator that allows players to choose which floor to visit.
Super-tall Skyscrapers If you are building your city in superflat, you can build extremely tall skyscrapers. If each of the floors in the building is 4 blocks high (including the floor), you could build up to 64 floors. If each floor in the building is 3 blocks high (including the floor), you could have up to 85 floors. If you have a mod that allows it, your skyscraper could go above layer 256 and make it even taller. Make a floor plan, such as:
Ground Floor: Lobby
Floors 1 through 5: Mall/Shopping Center
Floors 6 through 20: Offices
Floors 21 through 40: Apartments
Floors 41 through 61: Hotels
Floor 62: Observatory