Wieliczka salt mine - Poland

The attraction also houses a chapel, ballroom, restaurant, shops and a son et lumière experience

The Wieliczka salt mine is Poland's largest tourist attraction, and is made up of hundreds of miles of tunnels.

A sanatorium is located down underground and is frequented by asthma-sufferers, as it is known for having air free of pollution and allergen.

As well as the sanatorium, the attraction also houses a chapel, ballroom, restaurant, shops and a son et lumière experience with a Chopin soundtrack, all carved out of the solid salt rock.