The company behind the construction of the sprawling complexes, Vivos, says the facilities are for the "protection of high net worth individuals" in the event of apocalyptic-style scenarios during which "millions will perish or worse yet, struggle to survive as victims".

"Where will you go when pandemonium strikes?" asks a promo for the luxury shelters.

The biggest facility, called Europa One, is located in Germany and is "one of the most fortified and massive underground survival shelters on Earth, deep below a limestone mountain" and is "safely secured from the general public, behind sealed and secured walls, gates and blast doors".