When you think about urban landscapes, what first comes to mind would probably be the cities of New York, London, Paris, Beijing, Tokyo, or Barcelona. But over the course of history, different groups of people have also constructed cities underground. For whatever reason they built these cities, they are quite intricate and the design suggests that as many as tens of thousands used to live in them. Austin Harvey, from All That's Interesting, shows us 11 underground cities that would leave anyone bewildered as to how they were made and why.
(Image credit: Igor Sporynin/Unsplash)