WHEN Craig Denham purchased his Texas home, the previous owners shared some intriguing information: "There's a basement in the back, a shelter".

Curious, he headed down the steep stairs set in limestone at the back of his new home. Venturing into the darkness, he discovered an astounding time capsule which had been sealed from the outside world for 50 years - aside from one quick opening by the previous owners.

With a single light bulb, a shabby-looking toilet behind a shower curtain, an escape map pinned to the wall and a periscope "perfect for the zombie apocalypse", the fallout shelter is from the height of the Atomic Age, the Austin-American Statesman reported.

During the late 1950s and early 1960s, there was high anxiety among Americans about the prospect of nuclear war.

Concern turned to hysteria during Cuban Missile Crisis, a 13-day standoff between the US and the USSR in 1962 over missile placement in Cuba.

In the midst of the Cold War, fallout shelters were built to protect occupants from radioactive debris after a nuclear explosion.

This enclosure was originally built in 1961 by a retired air force colonel, E.V. Robnett Jr., who was also an inventor and died in 1984.

Mr Denham believed the colonel had access to information the public didn't.

The fact he built a shelter in his backyard shows "there must have been real concern with people's safety" during the time, Mr Denham said.

The previous owners had bought the home two years earlier from the colonel and his family.

"They took the hinges off," Denham said. "There was no electricity down there at the time, so they peeked in with flashlights and didn't remove anything".

When he bought the property in 2008, Denham sneaked back down the cold concrete stairwell. He figured out how to work the lights, removed the contents for cleaning then returned everything to its original place.

The Atomic Age buff maintains the shelter meticulously, taking pride in his unique space.

His daughters have played zombie apocalypse inside the musty chamber, but he has one unwavering rule.

With a serious look on his face, Denham said: "I've never shut the door behind me".