Villa Leopolda, French Riviera

Villa Leopolda on the French Riviera, originally built for King Leopold II of Belgium in 1902, sold in 2008 for $750 million — briefly the most expensive residential real estate transaction ever recorded. Set on 18 acres overlooking the Mediterranean between Nice and Monaco, its 11 villas, orangeries, and guest houses are set within one of the most elaborately landscaped private gardens in the world.