Top-secret super-secure Los Alamos vault declassified

Down in a remote canyon near Los Alamos National Laboratory lies a facility known as the "Tunnel Vault," once one of the most secret and secure locations in the United States, it's the original post-WWII nuclear stockpile storage area. Located in Los Alamos canyon at Technical Area 41, the Tunnel Vault was built between 1948 and 1949. The facility has a formidable security perimeter, a hardened guard tower — complete with gun ports and bulletproof glass — and a series of gates and doors that lead to a 230-foot long concrete tunnel that goes straight into the canyon wall. At the end of the tunnel is a large alcove room with a single bank vault door. Through that door is a vault built inside a vault with five storage areas, all protected with identical bank vault doors. Over the years the Tunnel Vault was also used as a nuclear materials and nuclear fuel storage area, a weapons research and development laboratory, weapons components storage, and nuclear material assembly for tests both in the Pacific and in Nevada. About halfway down the tunnel is a side room that was used for early development of unclassified research that led to the discovery of the solar neutrino — work that later won a Nobel Prize in physics — a lab space ideal for the work because it's buried 300-feet deep underground.