underground. >> you can choose your own view. >> reporter: there's a school room where the kids can continue their studies, even when it's not safe to go outside. >> who is the teacher? >> you, me, the other owners. >> reporter: that's part of the deal with the condo association. during a lockdown, everyone would work a four-hour shift, if not in the classroom, maybe in the store or the green house where they'll farm fish and organic vegetables. >> we'll have lettuce, celery, carrots, onions, blueberries, strawberries, kale. >> reporter: the thing you have to keep reminding yourself is why this place is here and why it's bristling with security measures, including air filters to neutralize a nuclear, biological or chemical attack. and an extensive armory with plenty of guns. >> this is ft. knox? >> this place is ft. knox. >> reporter: even at $1 million to $5 million a pop, the condos are completely sold out. larry took us to another silo where he's just getting started. >> a definite fixer-upper. >> reporter: deep underground. you get a sense what it was like the last time americans felt in imminent danger. >> this is like the wreck of the