For many conceivable shit-hits-the-fan scenarios, hiding underground is a good plan to have. Basements, tunnels and underground car parks are great, but even better is a massive cave complex. I mentioned the Louisville Mega Cavern in my book, and here’s another huge man-made underground hideout, this time in Nottingham, England – 500 caves, up to 1,000 years old:
The family attraction that is now the City Of Caves was made possible thanks to the soft Sherwood Sandstone beneath Nottingham that allowed hand-carved cellars to be excavated and used as store rooms, factories, pub cellars, dwellings and even air raid shelters. Most of the caves remain in private hands, and some were destroyed over time by various city developments.
By February 1941 86 caves in Nottingham were available as public shelters.
I haven’t been there yet, but I presume gaining entry in an emergency won’t be too difficult for a survivalist who has planned ahead. Safety from a meteor storm, nuclear strike, solar storm, supernova or whatever else takes your fancy.