This unusual view of downtown New York growing buildings from 1840 to 2020 (the animation includes projects under development) is the work of the aptly named Cube Cities, an urban-visualization service. The company creates computer-generated skylines for major cities based on property listings and Google Earth data, with similar videos for Chicago, San Francisco, Toronto, and elsewhere.
Cube Cities finished the Lower Manhattan project earlier this month. If you've got your browser plugins in order you can explore the air space around the ersatz city in three dimensions, like a seagull swooping through vividly colored canyons.
But the animation is cool enough as is: Watch as urban development sends structures leaping into the sky in the first couple decades of the 20th century, grind to a halt until the 50s, then go bonkers all the way to the new millennium.