Zadar Sea Organ
This is something you probably have never even heard of. There are actually a few sea organs in the world, and the one in Zadar, Croatia is incredible. The Sea organ is an architectural sound art object and an experimental musical instrument.
Source: YouTube
It plays music via sea waves and tubes located underneath the large marble steps. As waves crash over the tubes, harmonious sounds echo over the steps. So basically, the sea is the musician. Pretty cool, huh?