The Sea Organ in Zadar, Croatia is played by the wind and waves of the Adriatic Sea. The Sea Organ, or Morske Orgulje, is a 230-foot long instrument and an architectural marvel. Concealed beneath its long staircase are 35 pipes, which release notes through openings in the uppermost stairs. These notes are produced when the sea's waves and wind pass through the pipes, "playing" the instrument continuously. The organ was completed in 2005 by architect Nikola Bašić. Listen to the organ's eerily beautiful music in the video below, and learn about some other "instruments" found in nature.