I'm wondering if it would be possible to have a city designed entirely by one person, or a team of people that work together, and totally planned out before so much as a single brick is laid down. Massive living quarters erupt in one part of town, with easy access via subway or other mass transit to various shops and commercial areas, transportation to massive factories or other employing concerns, all of it extremely high density with extremely smart transportation systems so everyone gets everywhere quickly and with no massive pile-ups.
The buildings are extremely smart, and riddled with domotics. They have been designed to remain at a comfortable temperature with a minimum of energy use, and the built-in computers anticipate your needs and change things to meet your every whim. Sensors also handle security functions, locking up when you're not there, summoning police when signs of intrusion exist, and summoning the fire department when uncontrolled fire is detected. A smart grid attempts to shift energy usage to when it is cheapest.
Distributed power production minimizes line losses, and increases electrical reliability. Other services should also be, if possible, distributed. If no region is far from a police station, then commiting a crime in this city will be immensely difficult, if not impossible.
Recycling would be very prevelent. Instead of bothering with waste receptacles, there would be labeled chutes. Household robots would be able to identify wastes, and file them correctly. ("Here, robot, throw this away, kthx.") Heat and light would also be carefully crafted resources, moved to where they are most helpful. Even the most noxious waste, like blackwater, is quickly funneled away from people, and taken to distant water purification plants where the water is recovered, and the waste composted into organic fertilizer, in which we grow flowers. (Preferably without directly touching them. Ick.) With enough chemistry resources, there is a use for everything.
My only concern is that having designed all this, no one entity can afford to build it all alone. And building only part of it may lead to...problems. If the living quarters is built, but not the workplaces, then people will have shiny apartments that they can't afford the rent on. If the transportation system is neglected, then people will have to walk everywhere, because there's no room for roads with this many people. (And the footpaths will be unbearably crowded.) If waste management is neglected, this city suffocates beneath a layer of garbage. Its primary strength is the way that the entire system works together as a whole, and it is all designed by the best experts available to work together.