That's Olympus Mons behind the city. Olympus Mons is the largest volcano in the Solar System, over 25 kilometers tall and hundreds of kilometers across. At its base is a cliff several thousand meters high. The caldera at the top of the extinct volcano is about the size of the Hawaiian island of Oahu. When I was a little kid, I wanted to be able to climb that mountain. Who am I kidding? I still want to climb it.
As I write this, the European Beagle 2 probe has landed on Mars. The American Odyssey orbiter is due to pass over the Beagle's landing site and attempt to make contact. With any luck, we'll be getting pictures and science from the probe in a short while. I'm considering it a holiday gift..
I'm not so sure that Olympus Mons would actually look as impressive from the ground as it does in the first panel, exactly because it is so stupidly huge -- the mountain really exists at far beyond human scale. Dividing a 25-kilometer ascent by a two-hundred-kilometer distance means reaching the top could be more a matter of cross-country hiking than mountain climbing. But it's hard to tell at this range. Clearly, we have no choice but to pop on over and check for ourselves. Science demands it!
In other news, thanks to longtime supporter Faith Hicks we have a link banner now, so you have no more excuses for not linking to MoS. Again: science demands it!