The complex of tunnels was formed during the resistance war against French colonialists (1946-1948). Photo: Penwar

“A museum contains photography and artefacts from the war and shows a propaganda film that's either disturbing or amusing depending on your mood. Bizarrely, a shooting range invites visitors to try an AK-47”, says the website.

Photo: Innervietnam

Rounding out of the list include Derinkuyu underground city, Turkey,

Photo (Pakhnyushchyy.)

Photo:  Pakhnyushchyy

Qing Dynasty tombs, China,

Photo: Tarter

Photo: Panoramio
Mary King's Close, Scotland, Photo: Tony Marsh
Photo: Paul Dodds
RESO, Montreal, Photo: AlPetteway
Photo: YvesMarcoux
Capuchin catacombs, Italy, Photo: Traveltipy
Photo: Pinterest
Metro rail system, Moscow, Photo:  LingxiaoXie
Photo: Mordolff
Salzwelten salt mine, Austria, Photo: Salzwelten
Photo: Travelaway
Sewer Museum, France, Photo: Flickr
Photo: Huffpost
Warwick Castle dungeons, England, Photo: Alamy
Photo: Kaybee
Salina Turda theme park, Romania, Photo: Alamy
Photo: BI