When I was at TED in February, I told Joshua Foer, (author of Moonwalking With Einstein: The Art and Science of Remembering Everything) about the Chislehurst Caves near London, suggesting that it would be a good place to visit on Obscura Day (an international celebration of unusual places that Joshua founded), held April 28, 2012. Joshua looked it up and agreed.
Here's the dope:
Thirty-five kilometers and completely self-made, these “caves” are shrouded in mystery. While used to mine for chalk, some believe that the oldest section dates back to the time of the "druids." Another section is supposedly attributed to the Romans when they came to England in 43 AD. Even Napoleon III and Shakespeare have also been tacked on to the space.
By WWII, the cave was repurposed as a bunker for 15,000 British citizens. Not merely a shelter, it was an elaborate underground city with a hospital and chapel. Twenty years later, it became a concert venue for rock stars like David Bowie and Led Zeppelin.
Today the cave is frequently used as a set for science fiction and fantasy television shows.
[The purpose of Obscura Day] is to get people all over the world going out to explore the curious places near them, on one day. Last year, we had events in 103 cities around the world, on all seven continents (including Antarctica).
Also: Here's my video interview with Joshua from TED2012.