A secret of Cold War came to light recently with Los Alamos National Laboratory in New Mexico releasing a video tour of what was once one of the most secret and secure locations in the United States. For decades, Tunnel Vault was used to house nuclear weapon components, but the now declassified facility has now become an artifact of the Dr. Strangelove age.

The Cold War was arguably the single most important crisis in the second half of the 20th century, the outcome of which hinged not only on the question of which side would be the victor in the event that war broke out, but also whether civilization would survive at all. Los Alamos was pivotal in this story, but like so much connected with nuclear weapons and superpower intrigue, much of its history remains shrouded in secrecy, from its founding as the centerpiece of the Manhattan Project during the Second World War to develop the first atomic bomb to the present day.

The Tunnel Vault is one of these secrets. It’s located in Los Alamos canyon in a location known as Technical Area 41. Built between 1948 and 1949, it looks as if it could pass for a workshop where you’d find someone fixing cars or building boats. However, the giveaway is the security perimeter with a guard tower boasting bulletproof glass and gun ports.

Behind a mundane roll-up shutter is a series of gates and doors that reveal a 230-foot (70 m) concrete tunnel going into the canyon wall. You’d expect this to end at some cavernous, palatial office with a sinister bald man petting a white cat. Instead, there’s a room with vault door like something out of a bank or a diamond exchange. Behind this is another corridor with five more vault doors opening onto storage areas.

It was here that the materials for the first atomic weapons were stored during the first years of the Cold War. Later, as Los Alamos was converted from a rough, muddy camp to a permanent facility, the Tunnel Vault was used to store nuclear materials and components for thermonuclear weapons under development before being assembled for testing in the Pacific Ocean or the Nevada test site.

“This facility had a long history during the cold war. So this was definitely a top secret, very secure location,” says Ellen McGehee, the Laboratory’s historic facilities manage.

However, the Tunnel Vault wasn't just a weapons facility. It was also used for pure research, such as work that led to the discovery of the neutrino, which won the Nobel Prize for physics.

The video was released as part of the Los Alamos Laboratory’s 70th anniversary “Signature Week” last week, which saw tours of the vault for the media and the Laboratory’s employees and family members.

The Tunnel Vault story is outlined in the Los Alamos video below.

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