Derinkuyu, Turkey

de bene esse: literally, of well-being, morally acceptable but subject to future validation or exception

"Derinkuyu is an enormous, ancient underground city that dates back to the early Byzantine Empire. It's unknown when the city was begun — some sources say as early at the 7th century BCE — but it wouldn't have reached its greatest size until the period between 500-1000 CE, when it was five stories deep with room for 20,000 people, plus livestock, kitchens, a church, and a wine-making facility. Locals dug tunnels and rooms beneath their homes, deep into the soft, sandy volcanic rock of the central Turkish region of Cappadocia. An entire underground civilization was thriving here during the middle ages, which could provide a model for future communities trying to survive an apocalypse." - Annalee Newit