If you happen to be in Portland on a Sunday evening and in need of an adrenaline rush, grab your bike, helmet, lights and other protective gear, and hop the light rail to Washington Park Zoo, then take the elevator to the top. There you can join fellow cyclists--and maybe some skaters and longboarders--for an exhilarating Zoobomb!
Zoobombing involves riding bikes (or skates or skateboards) as fast as you can down West Hills. This event has been happening regardless of weather every Sunday evening since 2002 and is firmly ensconced in Portland's bike culture. Do a search on YouTube and you'll find tons of videos of this event. Sample one below.
Willie Weir and Kat Marriner recounted their zoobomb experience in a series of blurbs on their blog, Yellow Tent Adventures.