The Citadel of Aleppo is one of the wonders of the medieval world, but it's also endangered: Last year, its monumental iron doors were damaged in the fighting between Syria's rebels and government forces.
This view of one of the world's largest castles is one of DigitalGlobe's top 20 images of 2013. Vote for your favorites by hitting the "like" buttons on the company's Facebook album: The five most liked images as of Dec. 16 will move on to the finalist round for top image of the year. Right now, Aleppo is No. 1, but it's a close race. We'll be featuring more of DigitalGlobe's pictures in our own Cosmic Log Space Advent Calendar, which gives you a different view of Earth from space every day from now through Christmas. For still more holiday goodies, check out The Atlantic's Hubble Advent Calendar, Zooniverse's Advent calendar and the Galileo's Pendulum Science Advent Calendar.
Previously on the Space Advent Calendar:
- Day 2: Where the rain in Spain goes
- Day 1: Farewell, Earth ... Hello, Mars!
- 2012 Cosmic Log Space Advent Calendar
- 2011 Cosmic Log Space Advent Calendar
- 2010 Cosmic Log Space Advent Calendar
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.