Atlas Survival Shelters sells huge corrugated pipe shelters outfitted for living with air filtration systems, Co2 scrubbers, and power generators. A 10' x 20' shelter goes for $30-$40,000 and the "Hillside Retreat," a 10' x 51', runs as high as $109,000. Options include a big screen TV, electric fireplace, oak flooring, hatch camouflaged as a boulder, and many other fine amenities. From their pitch:
The only bunkers manufactured today that has actually been tested against the effects of a nuclear bomb and has passed, is the round corrugated pipe shelters (used in the 1950s) by the U.S. Army Corps of Enginneers..
The round shape worked then and still works today! 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.
"Beware the Square". No pre-manufactured square metal bunkers passed the nuclear test and should only be regarded as a fallout shelter or tornado shelter at best!