To the untrained eye, a set of stairs along the coast of Zadar, Croatia, looks like any other set of concrete stairs that lead to the sea. But to even the most untrained of ears, it's clear that these are more than just stairs.
They're actually a sea organ, an instrumental natural art installation that's part of an effort to restore the beauty of the sea to an area once ravaged by World War II.
After the destruction from the war, officials in Croatia scrambled to rebuild the area along the coast and wound up with an ugly but sturdy concrete wall. But in 2005, the city wanted to spruce up the coastline.
Part of that project meant hiring architect Nikola Bašić to transform the dull concrete. Bašić built a series of broad steps reaching out to the water.
The lowest steps allow water and air to flow toward them, and that water and air is then funneled into 35 chambers built into the steps, all of varying tilts, lengths and diameters.
The water and air flows through them and then is pushed out through channels on the higher stairs.
When that happens, visitors hear the low, chime-like undulations resonating through the air, producing music similar to that of an organ.
That's how it got its name, the Sea Organ. But unlike the musical instrument often found in churches, this organ doesn't require a human to make it play. Instead, it needs only the sea.
That means that, since the flow of the current is constantly changing, each sound that comes out of the sea organ is totally unique.
A thousand visits to the Zadar monument will result in a thousand different melodies you'll get to experience.