A stuffy, noisy mile-long secret Cold War tunnel is up for sale in London, asking price $7.4 million — it's only five minutes' walk from my office, too, connecting up Chancery Lane with the Thames. It's only got two lifts, which means you couldn't possibly get fire-code approval to run it as a hotel or club, but there's all kinds of intriguing possibilities (e.g. ball pit) for this much subterranean volume.
But it was not long before the documents had to be moved again to make room for a secure international telephone center that the government deemed necessary as relations between Washington and Moscow grew tense. During the cold war, the British government instructed its telephone department, which later became BT, to set up a secret communications system based on the latest technology that would be able to survive a nuclear attack.
It was the beginning of the busiest period for the tunnels, with almost 200 workers spending their days and nights underground to route up to two million calls a week across the 6,600 phone lines. In 1963, the hot line established between Moscow and Washington after the Cuban missile crisis ran through the London tunnels.
The buzzing complex soon became known as "underground town," with its own recreation room complete with dartboards and billiard tables, a movie theater and two dining halls. Workers often spent the night in sleeping rooms.
(Thanks, Organ Leroy!)