The Sea organ (Croatian: Morske orgulje) is an architectural object located in Zadar, Croatia and an experimental musical instrument, which plays music by way of sea waves and tubes located underneath a set of large marble steps.
Chaotic reconstruction work was undertaken in an attempt to repair the devastation Zadar suffered in the Second World War. The frantic reconstruction turned much of the sea front into an unbroken, monotonous concrete wall.
The device was made by the architect Nikola Bašić as part of the project to redesign the new city coast (Nova riva), and the site was opened to the public on 15 April 2005. The waves interact with the organ in order to create somewhat random but harmonic sounds.
The Sea Organ has drawn tourists and locals alike. In addition, white marble steps leading down to the water were built later. Concealed under these steps, which both protect and invite, is a system of polyethylene tubes and a resonating cavity that turns the site into a large musical instrument, played by the wind and the sea.
In 2006, the Sea Organ was awarded with the prize ex-aequo of the fourth edition of the European Prize for Urban Public Space.