Security was key to the design of the Federal Reserve Bank; so much so that an independent building was constructed around the bank's vault. Concrete walls 6.5 feet thick and interlaced with metal surround the two-story, 133-ton vault. The vault's door weighs 100 tons, has possibly the largest hinge in the world, and is more than five feet thick. Transportation of the door, which was manufactured in New York, required the nation's largest flatcar. In addition to the vault, the Federal Reserve houses its own power plant as an additional security feature. Independent of city utilities, the bank can generate its own electric power, steam, and air conditioning.