Look at these examples of hidden underground survival shelters that preppers are building across the country.
A fall-out shelter that is better than people's houses. This would make THE greatest Man Cave.
apocalypse bunker made from a former missile-silo, these could be a good idea,purchase them around the country if your a millionaire and have nice rest points for you travels during the z end of days lol(also can be used as an minecraft house I'd
Alternative to Shipping Containers: Use Box Culverts - SHTF, Emergency Preparedness, Survival Prepping, Homesteading Etc.
Underground bunkers can be your saving grace, but only if built correctly. Survival Life is the best source for prepper survival gear, tips and skills.
Customer satisfied with BuildBlock ICF storm shelter
Shipping Container Makes an Amazing Underground Shelter/Wine Cellar