From war rooms in London to below the ground sanatoriums in Poland

Attractions include underground theme parks, trampolines and cathedrals

MailOnline Travel has compiled the best of the best from Wales to Australia

From the skeletal remains of six million Parisians to a theme-park buried in the depths of one of the oldest salt mines in the world.

These are some of Earth's best underground attractions that are hidden in the shadows beneath the surface.

Here MailOnline Travel compiles the best of the best including an eerie world of underground living in Australia to neon trampolines and slides in Wales.

Catacombs of Paris - France

Empire of the dead: While much of the 200-mile network is out of bounds, a small section is open to tourists