Clap in Front of This Pyramid and a Bird Answers

Stand at the bottom of the main staircase of a Maya pyramid in Mexico, clap your hands once, and something chirps back at you.

The echo isn't a plain echo. Each step bounces the sound back at a slightly different moment, so the one clap comes back as a quick string of notes, which seems to go higher as it fades. Researchers recorded it and compared it to the call of the quetzal, a bright green bird the Maya held sacred. It sounds a lot like it. The pyramid is called El Castillo, "the castle," or the Temple of Kukulkan, and it stands in the ruins of Chichén Itzá, in the Yucatán.

Kukulkan was a feathered serpent, one of the most important gods of the region. And twice a year, once on the day in spring and once on the day in autumn when day and night are the same length, the pyramid seems to bring him to life.

Late in the afternoon of those days, the sun shines on the corner of the pyramid at a sharp angle. The edges of the steps cast a row of triangles of shadow down the northern staircase. At the bottom of the staircase there's a carved stone snake's head. So the zigzag of shadow looks like the body of a snake, and as the sun moves, the shadow slides slowly down the stairs toward the head. It lasts for a few hours, and thousands of people come to watch.

The pyramid has numbers worked into it, too. It has four staircases, each with 91 steps, and if you add the platform on top as one more step, it comes to 365, the number of days in a year. It's about thirty meters tall, built by the Maya around a thousand years ago. The same site has the biggest ball court known in the ancient Americas. It also has nine stepped levels, which the staircases split into eighteen sections. People often point out that eighteen is the number of months in one of the Maya calendars.

There's something else, hidden inside. When archaeologists dug into the pyramid, they found that it was built over an older, smaller pyramid, like one of those nesting dolls. Inside that one they found a throne carved in the shape of a jaguar and painted red, with spots made of jade.

Did the builders plan the snake and the chirp? That's the honest question, and nobody really knows. Some people think the shadow was clearly deliberate, given how well it lines up with the equinox. The chirping echo might have been a happy accident, or it might not. There's no Maya text that explains it.

The steps are real, though, and you can count them yourself.