This satellite image from GeoEye highlights the Maya pyramid known as El Castillo, or the Kukulkan Pyramid, the focal point of a monumental plaza at Chichen Itza on Mexico’s Yucatan Peninsula. The pyramid was apparently constructed with an eye to the calendar: During the spring and autumnal equinoxes, patterns of sunlight move across the main stairway to make it look as if the body of a serpent (Kukulkan) is creeping downward to join up with a giant serpent’s head carved in stone at the bottom.

Each of the stairways has 91 steps, and when you add the platform at the top, the total comes to 365 steps — the number of days in a year. The Maya, of course, were expert calendar makers. The fact that their “long count” calendar comes to an end in 2012 has led some to fear that the world will end. But even present-day Maya say that’s silly. It’s merely the end of a cycle, just as we’ll be ending a calendrical cycle in just a couple of weeks. We’ll see.

Chichen Itza on Mexico's Yucatan Peninsula