That's a crater in the middle of Derweze, which is a village in Turkmenistan. And it's on fire. It's been on fire for 40 years.
Here is the Wikipedia page; there's not a ton of information, but I guess enough to give context. In 1971, this crater formed while some people were drilling, and they realized that methane was emanating from it. Geologists decided that burning the gas would be less dangerous than letting it permeate the atmosphere, and figured that it would burn out in a matter of hours. It's still burning.
Isn't that nuts? The crater (which is 230 feet across, by the way,
I immediately put the town's name into Metafilter, because this is exactly the sort of thing that would be posted in there. And, you know what, not really. Why don't more people talk about this thing?
Check out some more pictures on Flickr.