The Burlington Bunker is a 35 acre underground complex built into a disused quarry in Wiltshire to shelter the British government in the event of a nuclear attack. It was built to accommodate 4,000 people for at least three months, and had its own generator, kitchen, bakery, two canteens, laundry, infirmary, dentist, offices, living areas, telephone exchange and television studio – all connected by 10 miles of underground roads that the inhabitants would navigate in a fleet of electric buggies.

It was never used and pretty much hasn't been touched since it was decommissioned in 1991. The site I linked above has some great pictures of the rooms, complete with their original 1950s fixtures.