The Pyramid That Chirps

At Chichén Itzá, the old Maya city in Yucatán, Mexico, stands a great stepped pyramid called El Castillo. Visitors often try a little trick there. If you stand in front of its main staircase and clap your hands once, the echo that comes back does not sound like a clap. It sounds like a bird's chirp.

The secret is in the steps. The sound of your clap hits each step and bounces back to you. The higher steps are farther away, so their echoes arrive a tiny bit later than the lower ones. All these small echoes blend together into one sound that changes pitch, like a chirp.

In 1998, an American sound expert named David Lubman listened closely and made an interesting suggestion. He said the chirp sounds a lot like the call of the quetzal, a bright green bird with very long tail feathers. The quetzal was a very important bird to the Maya, and its feathers were highly valued.

So did the Maya build the chirp on purpose? Experts do not agree. Some think the builders shaped the steps to make this special sound. Others point out that many tall staircases make similar echoes, so it may be a happy accident. Either way, visitors still love to stand at the bottom and clap.