Fairfield Pond (United States) - Completed in 2003 - Height: N/A

Detail: Owned by billionaire Ira Rennert, this mansion in the Hamptons is one of the largest privately-owned homes in the U.S.

Interesting Fact: It has its power plant to ensure an uninterrupted power supply. It's estimated to be worth over $248 million, making it one of the most expensive homes in the US.