President of the UAE and hereditary ruler of its capital emirate, Abu Dhabi.
UAE is home to one-tenth of world's oil reserves; petrodollars-dollars are the president's family's original source of wealth. His real estate also is becoming more valuable, as property values rose 100% from 2005 to 2007.
Sheikh Khalifa spent more than $1 billion--including $200 million on a Frank Gehry-designed Guggenheim museum--on branding Abu Dhabi as a cultural center.
Abu Dhabi Investment Authority recently made headlines by investing $7.5 billion in Citibank and buying New York's Chrysler Building for $800 million.
Ascended to the throne August 2005; soon after, construction began on a $26 billion city named in his honor, which the government hopes will become the new economic epicenter of the Middle East.
Saudi Arabia is now earning approximately $1 billion a day from oil exports, helping boost the royal family's fortune. The king is an avid horseman and breeds Arabian horses; he founded the Equestrian Club in Riyadh.