Where do you store your image archive? A file cabinet? Drawer? Or maybe archival safety is really important to you and your images are tucked away inside a moisture-controlled fire safe? The chances are you didn’t say 'inside a former limestone mine', which is where Corbis Images keeps its Bettmann Archive, a collection of more than 11 million historical images. 

A documentary called 'The Invisible Photograph' created by the Hillman Photography Institute of the Carnegie Museum of Art explores the old mine in Boyers, Pennsylvania and the sub-zero photographic archive Corbis created there.

Iron Mountain, a data management firm, and Corbis created a 20,000 sq. ft temperature controlled storage facility that’s more than 200 ft below ground where its kept at -20 degrees celsius. The exact climate for the archive was developed by film storage pioneer Henry Willhelm, who is seen in the video touring the facility and clearly enjoying the fruit of his labor. It’s estimated that the collection will last five hundred times longer in this cold storage facility than it would have in the previous archive in New York City. 

The Bettmann archive started when Otto Bettmann fled Nazi Germany with suitcases packed full of 15,000 images. It grew to become one of the largest and most important collection of images, with work spanning back to the 1800s and includes some of the world’s most iconic images – Rosa Parks seated in the front of the bus, Marilyn Monroe with her skirt blowing up and Einstein sticking out his tongue.

The archive acquired several collections in the 1960s through 1980s, and then was acquired by Corbis in 1995.