Hidden in the sleepy Turkish town of Derinkuyu hides a vast underground city that once housed 20,000 people. Dating back thousands of years, the 18-storey subterranean marvel is 280 feet deep and has stables, granaries, kitchens, dwellings, a school, a church and more. 

Click or scroll through to explore the supersized labyrinth, find out why it was abandoned and how much we still don't know about this mysterious place...