The Iron Mountain storage facility is a high-security storage facility in a former limestone mine at Boyers, Pennsylvania, near the city of Butler in the United States. It was used to store records beginning in 1954, and was purchased by Iron Mountain in 1998. It is here that Bill Gates stores his Corbis photographic collection in a refrigerated cave 220 feet (67 m) underground. Nearby, the U.S. Office of Personnel Management leases another underground cavern to store, and process government employee retirement papers. Continue reading to see more of the world’s most secure locations.