Why do people go underground? To escape enemies? To hide from the sun? Or to seek something that others must not know about?
Entire cities exist deep within our planet. Thousands of people have lived — and still live — where the sky is a stone vault, and the streets are dark tunnels.
Some of these cities were carved out in desperation. Others — driven by the pursuit of gold, knowledge… or salvation.
But what if these labyrinths hide more than we can imagine? Today, we venture into the fascinating subterranean worlds. The places where the day ends and eternal darkness takes over.
30 Underground Cities.