3. Villa Leopolda -- $750 million 

This palatial series of villas and gardens located in the town of Villefranche-sur-Mer on the French Riviera was once owned by King Leopold II of Belgium. It made the news in 2008 when Russian billionaire Mikhail Prokhorov was forced by courts to forfeit a €39 million ($48.34 million) down payment he made to owner Lily Safra after a price dispute scuttled a deal for the home. Safra donated the money to various philanthropic causes around the world. She inherited her fortune from her husband, the late banker Edmond Safra.