The underground cities in the region of Cappadocia are very old, some apparently dating back to the time of the Egyptian pyramids. Carved from the region’s volcanic tuff, some of these underground cities are connected by tunnels that run as long as four or five miles. That’s a bunch of excavating. “What are you doing today?” “Digging. Tomorrow, too.”
Obviously, people dug, and dug, and dug for a reason, and that reason was no different from the reason people dug bomb shelters during the last century: Safety. Safety has always been a concern, and, if you think about it, in seeking safety, people aren’t too different from meerkats. There’s some safety in living beneath the surface. But such a life also has its drawbacks.
When the United States government sought underground facilities for surviving a nuclear war, it built an underground hideaway at the Greenbrier in West Virginia. Not bad. Got your resort right there, very convenient unless there’s an actual attack. The government also looked into storing food and finding shelter in Mammoth Cave in Kentucky. Now that’s a big hole, and nobody has to do any digging.
Unfortunately, every place on Earth and under Earth has its drawbacks with regard to safety. Mammoth Cave, for example, has multiple places for air to enter, and such air would carry any surface radiation into passageways. But just being underground poses many problems even without nuclear fallout. There’s the darkness, for example. And in Cappadocia, the rocks contain erionite, a mineral known to cause mesothelioma and suspected to cause lung cancer.
So, there they were, those generations of rock excavators, carving by hand the volcanic tuff not just for a day, but rather for years, decades, and, if reports are correct on the most recently discovered underground city, millennia. That much digging exposed many people to erionite (Na2,K2,Ca)2Al4Si14O36·15H2O. The very walls of their underground cities were a threat.
That reminds me of a story a classmate from Brazil told during an ichthyology class on dangerous fish. His uncle was attacked by killer bees. To escape, he dived into the river, where piranha ate him. Know the place where you seek safety.