The Gold Vault marked its 50th birthday in 1986 and is among the most well-known buildings in the United States. Yet, the building wasn't added to the National Register of Historic Places until February.

That list includes many thousands of places - buildings, bridges, sites - in the United States. Most are less famous than the Gold Vault, which is referred to in books, movies, television series and even in casual conversation: "Gosh, I bet he's got more money than all the gold at Fort Knox."Though shrouded in secrecy, the Gold Vault is believed to contain half of the country's gold. And some art experts also believe some paintings, jewels and other items confiscated in Europe at the end of World War II remain there.

The Gold Vault is a favorite tourist attraction. Federal officials, who try not to acknowledge the interest in the facility, may not realize that hundreds of people actually come here and believe they can tour the place.

The lobby is reportedly made of local marble with ceilings that feature intricate molding, chairs of polished wood and a pew. That description was given by a former employee, who retired in Radcliff, Ky.

He said the lobby also features a display of medals and plaques the security personnel have won in government pistol competitions. The Gold Vault is reputed to have in its basement a pistol range used daily for practice.

So you think the U.S. Bullion Depository, as it is officially known, is part of Fort Knox?

Wrong. But don't worry. You're among thousands, maybe millions, who believe that.

The Gold Vault is actually on federal land and is operated by the Bureau of the Mint under the U.S. Treasury Department.

About 100 media representatives and 12 members of Congress were allowed to glimpse the front wall of some 36,236 gold bars in a 1974 tour designed to dispel rumors that there was no gold in the vault.