Along the main street, the signs in the median aren't advertising homes for sale; they're inviting employees with top-secret security clearances to a job fair at Cafe Joe, which is anything but a typical lunch spot.

The new gunmetal-colored office building is really a kind of hotel where businesses can rent eavesdrop-proof rooms.

Even the manhole cover between two low-slung buildings is not just a manhole cover. Surrounded by concrete cylinders, it is an access point to a government cable. "TS/SCI," whispers an official, the abbreviations for "top secret" and "sensitive compartmented information" - and that means few people are allowed to know what information the cable transmits.

All of these places exist just outside Washington in what amounts to the capital of an alternative geography of the United States, one defined by the concentration of top-secret government organizations and the companies that do work for them. This Fort Meade cluster is the largest of a dozen such clusters across the United States that are the nerve centers of Top Secret America and its 854,000 workers.