If you’re going to build a bunker to survive the zombie apocalypse, why not do it with some style? Atlas Survival Shelters are the only bunkers manufactured today that has actually been tested against the effects of a nuclear bomb.
There is little difference between the bunkers made 50 years ago and the bunkers made today except the addition of modern interiors, NBC air filtration systems, Co2 scrubbers, generators, and high-tech electronics. There is no other shape other then round that will allow you to reach the depth underground that you need for maximum protection for your family and to allow the climate to be controlled underground.