"A Sound Garden" is an huge musical instrument and art installation created by Douglas R. Hollis, on the National Oceanic and Atmospheric Administration Western Service Center campus.
Located on a hill overlooking Lake Washington in Seattle, the giant pipe-like structures murmur, whistle, and howl when the wind blows through them. The Seattle band Soundgarden famously named themselves after the Hollis piece.
Other art installations on the NOAA campus include works by such artists as Scott Burton, Martin Puryear, and Siah Armajani.
Visiting the NOAA campus is free, but security is tight. Make sure to bring a photo ID with you in order to get a day pass, and be prepared to have your bags searched. You also have to park your car and hike about a half mile to get to the art installations. The walk is well worth it.