This lovely short film presents an original scenario for a future interface to virtual world making. Like the famous Apple Navigator film from decades ago, or ATT's You Will series of ads, or the Minority Report's scene of transparent gesture interface, this fictional depiction is convincing and inspiring. I want one now.
There are elements of the Google Sketchup interface taken to an extreme. I think it works.
Also, the film has a lovely narrative arc, which aids in the fantasy. The film was made by Bruce Branit.
UPDATE: Stewart Brand brought to my attention a real-world case of world-building. Here is a back-story video showing off the making of a 1,200 building city (7 million polygons in MODO) for a Toyota/Lexus commercial created by the design firm Hook.