In this day and age, grave danger is everywhere. Quite aside from the exponential toll of terrorism, there’s environmental catastrophe to consider, and so many potential vectors of deadly infection that just counting them could kill you—never mind the nukes pointed at every major population centre on the planet.
That the world will end—and sooner rather than later, some say—is as good as a given. Something’s got to give, and when it does, you and your loved ones will want somewhere safe to stay. Somewhere completely sealed against sickness; somewhere with such state-of-the-art security that not even a mouse could get into your house; somewhere so darned deep underground that surviving the bombs that are sure to start dropping is guaranteed to be a breeze.