Location: Bletchley Park, Buckinghamshire, UK
Reason to visit: German Enigma code was cracked here during WWII
During World War II, the British mathematicians and code experts at Bletchley Park, near what's now Milton Keynes, worked tirelessly to successfully crack the pesky German Enigma code, which was vital in defeating German U-boats in the Atlantic. Think Google Code Jam, only with lives depending on it.
Station X, as the Park was known at the time, was the main code-breaking establishment in Britain.
Now a museum dedicated to the code-breakers that once operated there, Bletchley Park sits as an interactive memorial to the efforts of heroic would-be Google employees.
Last year, the original machine that helped crack the complex German code was restored to working order. Google is rumoured to be interested in buying the mechanical algorithm. Also Microsoft.
Further Reading: here
Google Earth link: here
Google Maps link: here


