Sometimes things are just really cool to watch, like this video of the Manhattan Bridge moving along with the subway traffic.

A little history lesson from, um, Wikipedia—many moons ago, "because tracks were on the outer part of the bridge, passing trains caused the bridge to tilt and sway. The wobble worsened as trains became longer and heavier. The New York City Department of Transportation failed to maintain the bridge properly, and the tracks finally were closed [in the 1980s] for repairs. On February 22, 2004, the north side reopened, and all four tracks were in service simultaneously for the first time in 18 years." But don't worry, this swaying is totally normal, in fact, we'd love to see a time lapse of the Golden Gate Bridge during a strong wind... engineers built that one so that it could swing sideways up to 27 feet! [via Chrysanthe Tenentes]