Video: Top 10 Mysterious Underground Cities

Explore the unknown as we delve into the depths of the earth to uncover the top 10 most mysterious and fascinating underground cities that exist.

1. Derinkuyu, Turkey

Derinkuyu, Turkey

This ancient multi-level underground city could accommodate up to 20,000 people.

2. Beijing Underground, China

Beijing Underground, China

Built for the purpose of warfare, now serves as a tourist attraction.

3. Coober Pedy, Australia

Coober Pedy, Australia

Known as the 'opal capital of the world', the majority of the residents live underground to escape the extreme heat.

4. Wieliczka Salt Mine, Poland

Wieliczka Salt Mine, Poland

This underground city consists of a labyrinth of tunnels, the oldest of which date back to the 13th century.

5. Seattle Underground, USA

Seattle Underground, USA

After the Great Fire of 1889, Seattle was rebuilt over the top of the ruins, creating an underground city.

6. Edinburgh Vaults, Scotland

Edinburgh Vaults, Scotland

Once used as residences for the poor and even as venues for illegal activities, they are now a popular tourist spot.

7. Burlington Bunker, England

Burlington Bunker, England

This city was designed to house the UK government in case of a nuclear war.

8. Petra, Jordan

Petra, Jordan

This archaeological city is famous for its rock-cut architecture and water conduit system.

9. Catacombs of Paris, France

Catacombs of Paris, France

This underground ossuary holds the remains of more than six million people.

10. Shibaozhai, China

Shibaozhai, China

A 12-story pavilion was built against a 200 meter cliff in the Qing Dynasty.