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.

This view of Chichen Itza represents today's offering for the Cosmic Log Space Advent Calendar, which presents daily images of Earth from space through Christmas Day. For a wider perspective on Chichen Itza, check out this Ikonos satellite image. (Can you spot the swimming pools and the baseball diamond in the full-resolution image?)

For more Advent calendar goodies, check out the Web links below:

• The Cosmic Log Space Advent Calendar so far
• Door 1 for Dec. 1: Shuttle in spotlight
• Door 2 for Dec. 2: 'Alien' lake seen from space
• Door 3 for Dec. 3: Egypt's river of light
• Door 4 for Dec. 4: Tallest building reaches for the sky
• Door 5 for Dec. 5: Russia's dazzling delta
• Door 6 for Dec. 6: Space skipper vs. the world
• Door 7 for Dec. 7: Pearl Harbor from the heavens
• Door 8 for Dec. 8: Listening for E.T.
• Door 9 for Dec. 9: Blast from the past
• Door 10 for Dec. 10: Volcano caught in the act
• Door 11 for Dec. 11: Chronicling climate change
• Door 12 for Dec. 12: Happy St. Lucy's Day
• Door 13 for Dec. 13: Viva Las Vegas
• Door 14 for Dec. 14: Don't wake the volcanoes
• The Big Picture at Boston.com: Hubble Advent calendar
• Planetary Society: Solar system Advent calendar
• Zooniverse Advent calendar