"Urban exploration, also known as urbex, building infiltration and urban spelunking, is a movement that flies under the radar in a bid to investigate and photograph abandoned buildings and places, which often comprise the modern ruins of our recent industrial, military and civic past."
A further introduction to the concept can be found here, along with a whole host of articles on kinds of places to look for (like ghost towns and abandoned cities, abandoned mega-machines, and a random airplane tail left over from the Falklands War).
It doesn't stop at abandoned places, though. The site (and, presumably, the practise) extends to other interesting things created by man, like the California's Glass Beach, a Walk-In Roller Coaster in Germany, and Architecture on Scotland's Isle of Tiree.
It should not be surprising there is much to find in Great Britain:
And that's just the beginning.
We're watching a movie under the duvet this weekend. We hope you're doing something else.