Who knew? City building videos are a sub-genre.
Besides the two worldbuilding videos posted earlier, reader Branislav Ulicny sent along another cool example. This one is from a Swiss company that makes software to automatically populate cities with certain styles of buildings based on parameters chosen by the designers. As Ulicny says: "The difference compared to Sketchup-like interface of Worldbuilder is that their system "knows" what type of a building (or city) is needed, so that the interface can be even easier - you don't have to build everything from geometric primitives, you can just modify the parameters." In other words you set the design "grammar" of the buildings and it generates variations of those types of buildings, a variation you can simply "dial" to alter. The result is a hugely diverse yet harmonious city, constructed very quickly. It's sort of like a very smart SimCity.
Because the software works via procedures the company is called Procedural. Their software, CityEngine Software, is expensive pro tools meant for urban planners; runs on Windows, Mac and Linux. Free one month trial.
In the video below, Rome is re-constructed quickly via a "grammar" that makes Rome-ish buildings. The CityEngine software can also mapped out their placement generatively as well. The artificial city "grows" organically. This is how I would make a city if I had to.