Under the Wiltshire campaign, a 14-hectare underground complex called Spring Quarry lies 37 meters beneath the town of Corsham. Originally a Bath stone quarry, it was acquired by the Aeronautics Production Ministry in 1940 for the construction of an underground aircraft engine factory. In 1955, with approval from then-Prime Minister Anthony Eden, the site was transformed into a government war headquarters. Designed to house 4,000 people for three months in the event of a nuclear war, the complex included BBC studios, kitchens, and even royal apartments. Though it remained on alert throughout the Cold War, it was never activated. The site was given several code names, including Stockwell, Subterfuge, Burlington, and Turnstile. Initially, the conversion was estimated to cost 100,000 pounds over six months, but by 1945, the cost had ballooned to several million pounds, and the final structure fell short of original plans. The work involved removing thousands of tons of rubble and reinforcing the structure with steel and concrete. The complex features more than 97 kilometers of underground roads—roughly the distance between Paris and Chartres—and spans 14 hectares, equivalent to twenty football fields. Its depth is comparable to a twelve-story building buried upside down. Inside, the complex housed the second-largest telephone exchange in the United Kingdom, a BBC studio for the Prime Minister’s speeches, an underground lake, and a water treatment station. Four generator sets provided electrical independence, and a pneumatic tube system transported messages between different sections. The Prime Minister’s quarters included a residence, a card room, and a briefing room, while apartments were reserved for the royal family. After the site was declassified, visitors found frozen places, including a perfectly preserved manual telephone exchange, a communication center with over 700 teletypewriters, and large kitchens equipped in the 1960s but never used. The complex became obsolete shortly after its construction due to the growing threat of intercontinental ballistic missiles and the development of alternative plans, such as PYTHON. In 1989, part of the quarry was sold to a wine merchant named Octavian, and the site was officially declassified in December 2004. It was put up for sale in 2005, having been one of the most secret locations in Great Britain for nearly 50 years. Today, its neighboring galleries store wine. Historic England has designated nine areas of the bunker as listed monuments, granting the complex official protected status.