Kapadokya, Turkey is home to hundreds of linked rooms that, together, form an ancient system of underground cities over 2,500 years old.

Pembrokeshire, Wales is home to a family with a house straight out of The Hobbit.

Edinburgh, Scotland has a long and strange history, though perhaps the oddest story of all is the tale of a bridge that was buried underground.

Tokyo, Japan is at the heart of a strange and gripping mystery involving seven riddles and a supposed secret underground city. It all began when Japanese researcher Shun Akiba found an old map of the Tokyo tunnel system that didn’t match current maps.

Seattle, Washington’s Pioneer Square district has a very peculiar historical quirk: a century ago, they raised the streets by an entire floor.

Wieliczka, Poland sits atop one of the world’s oldest salt mines, in continuous operation for over 800 years until just this year.

Xi’an, China is now famous for featuring the Mausoleum of Qinshihuang