Swimming pools have become a standard fixture in basements for the the uber-wealthy. Orbital Basements It's no secret that London's property market is out of control: The city's super-wealthy are splashing their cash on levels of luxury most of us can only dream of — including £30 million bomb-proof townhouses and ultra-modern mansions on billionaires row.

But with land a scarce commodity and restrictions limiting how high you can build, what do the über wealthy do when they run out of room?

They build downwards.

Luxury basements have riled the city's property market for years now. Developers are attaching millions of pounds worth of extra value onto already pricey property by creating underground lairs with swimming pools, cinemas, saunas, and wine cellars.

While a single basement level is enough for some, others have multi-level basements that stretch as far as five floors underground. These "iceberg basements" are so-called because such large portions of the house sit underground.

We decided to take a look inside some luxury bunkers to see what all the fuss is about. All the plans we've included in this article have either been approved or are pending approval for construction from London councils.