On a pine-fringed 82-acre lot just northeast of Washington sprawls the capital's third largest, most tightly guarded building. Though smaller only than the Pentagon and the State Department, the modernistic nine-story headquarters of the U.S.'s biggest intelligence organ, the National Security Agency, is also official Washington's least-known edifice.
Protected by rings of electric wire outside and pistol-packing Marines within, NSA is a cathedral of cryptography—the occult art of secret codes. Bigger even than the Central Intelligence Agency, NSA headquarters houses about 14,000 employees, including some of the best analytic, mathematical and communications brains in the U.S. CIA's well-known headquarters in Langley,...
