Villa Leopolda, French Riviera

Villa Leopolda on the French Riviera was purchased for $750 million in 2008, a price per square foot of $7,500 that makes it nearly three times costlier than the average luxury villa in Monaco. Originally built for King Leopold II in 1902 on 18 acres overlooking the Mediterranean, its 11 villas and guest houses are integrated within one of the world's most elaborate private gardens. This residence outshines #3 Farnsworth House in size by 40 times, featuring an orangery that matured over 50 years.