30 years ago (and a few days), Reactor #4 at the Chernobyl Nuclear Plant in Pripyat, Ukraine had a meltdown. The explosion left the radioactive core entirely open to the world until they built the Sarcophagus , which is a big old (now crumbling) concrete bunker around it. So, lots and lots of Bad Nuclear Stuff was in the air, and as a result, the Chernobyl Exclusion Zone was formed for a 30 kilometer radius around the plant. The only people who still live there are the ones who refused to leave their homes, though some have become very sick as a result. Here's a selection of the first photos taken at Chernobyl; the pictures are foggy like that because that's what radiation does to camera film.
The interesting thing about the zone, though, is how it's affected the wildlife.
(Chernobyl sign from Wikimedia commons)