The plans also include a conference and communications room, hospital and dental surgery within the facility.

Designed for just one buyer, the bunker will ultimately be made to fit the specifications of its billionaire owner. It's not clear if the shelter has become a reality yet, or if it ever will – The Guardian has claimed the plans are no more than a "CGI pipe dream", or perhaps the project is simply being kept under wraps.

Oppidum has since expanded its catalogue to offer a range of ultra-luxury designs for its discerning clientele to choose from. These range from the bijou two-bedroom Model Linear starting at $8 million (£6.3m), right up to the extraordinary five-bedroom, seven-bathroom Model L'Heritage. Let's take a look around...

Billionaire bunkers made for the end of the world