$1.1 Billion Streets of Monaco Yacht

Currently in the concept stage, the Streets of Monaco yacht is set to become the world's most expensive at a cost of over $1.1 billion to build.

Yacht Island Design modeled the super ship after a section of Monte Carlo, and it will feature smaller versions of the state’s famous landmarks such as the Hotel de Paris and Monte Carlo Casino and racetrack. Swimming pools, tennis courts, a cinema, and go kart track will also provide an endless amount of entertainment.

You're not likely to own one of these but you can read more about it at My Modern Metropolis