The Wave Organ is a huge musical instrument situated on a Jetty in the San Francisco Bay. This ocean-powered organ was built in 1986 by artist Peter Richards, in collaboration with the Exploratorium. It was built from carved granite and marble that came from a demolished cemetery. The part of the organ that makes sound is built from over 20 PVC and concrete pipes. The pipes stretch down into the water and amplify the sounds made by the surrounding waves. If you're planning to visit The Wave Organ, keep in mind that the acoustics can only be heard when the tide is in. It's best to visit during high tide.