] It's nice down here, 220 feet below ground. It's dry and
] cool -- a springlike 60 degrees Fahrenheit. There is a
] breeze coming through the tunnels that smells like dust
] and something older than dust, the souls of the limestone
] miners, maybe, who began dynamiting this catacomb into
] existence 101 years ago.
]
] The only sound is a constant low thrumming, like the din
] of a ship's engine. There is a narrow roadway no wider
] than a country lane. A service van drives by, and then an
] electric golf cart. There are security guards, too,
] around every corner.
]
] "Keep it with you at all times," the guard at the gate
] had said, passing a fire extinguisher into the car as
] he'd waved me ahead toward a dim gray plaza, from which a
] maze of identical-looking gray tunnels snaked off in
] every direction.
]
] A fire extinguisher?
]
] Welcome to Iron Mountain, the largest commercially owned
] underground storage facility in the world. This is where
] Bill Gates, founder of Microsoft, has deposited his huge
] and growing collection of historical photographs --
] approximately 11 million negatives, prints, slides -- a
] cache that represents a culturally significant chunk of
] the visual history of the 20th century.

Buried Treasure (washingtonpost.com)