Conceived in 2005 by architect Nikola Bašić, this gigantic "sea organ" has been welcoming tourists and cruise ships to the charming port town of Zadar, Croatia. At a glance, it looks like a normal set of marble steps that lead to the sea, but upon closer inspection, each step holds five organ pipes turned to a different chord.

Waves and wind push air through these channels, creating a unique song. Visitors have called the sound "hauntingly memorable" and "rather rhythmical, even hypnotizing."

This sea organ is an amazing feat of architecture in one of the world's oldest cities. Zadar dates back 3,000 years and was nearly destroyed during World War II.