Upon moving back to Seattle in 2000, one of my favorite discoveries was the Sound Garden, a public art project built by Doug Hollis in 1982 and 1983. It's on the grounds of the National Oceanic and Atmospheric Administration (NOAA), which adjoins Magnuson Park, a huge Seattle park that used to be a naval air station.
The Sound Garden consists of 12 towers, each with an attached contraption consisting of a hollow metal pipe and a metal fin or rudder. The rudders catch the wind off Lake Washington, and the contraptions rotate around the central pole of each tower so the pipes are aligned accordingly. The wind blowing over the top of each pipe creates an eerie, breathy low note. Each pipe is a slightly different length, and as you traverse the path among the scuptures, you hear lots of interesting harmonies and dissonances. The sound is so otherwordly and inspiring that the Seattle rock band Soundgarden named themselves after it.
After the terrorist attacks of Sept. 11, 2001, the government shut the NOAA to public access entirely, locking the Sound Garden behind a fence with a chain around the gate. On windy winter days, it's still possible to hear it faintly from the public park several hundred feet away, but most of the time it stood alone and kind of sad. (If a sound scupture in a public space has no listeners, does it still make a sound?)
Today, I discovered they've finally reopened the gate from Magnuson Park. It's only open from 11:30 to 1:30 Monday through Friday, and a guard checks your driver's license and asks for a phone number, but at least you can experience it again. Highly recommended for anybody visiting Seattle. Here's a map (click "hybrid" for the best view).