The stalacpipe organ in Luray Caverns in Virginia pounds stalactites with electronically-controlled rubber mallets to produce its music. (Trevor Cox)
The World War II abandoned oil storage tanks in Inchindown, Scotland was the test site for the world’s longest echo. (RCAHMS)
A spot under archways at Grand Central Station in New York reflects the sound from the walls to the opposite side of the underpass and is called the Whispering Gallery.
The Mayan Pyramid at Chichen Itza, Mexico creates a chirp like the sacred quetzal bird if you clap your hands while descending the stairs.