François Pinault (#39): Palazzo Grassi, Venice

With a villa in St. Tropez (where he recently hosted his friend, ex-president Jacques Chirac), a 17th-century chateau near Montfort-L'Amaury and a penthouse in the Barbizon/63 building on New York City's Lexington Ave., this French fashion-retail mogul and contemporary art collector nonpareil has plenty of living space to adorn with painting and sculpture. But not quite enough room to house the thousands of pieces in his collection. And so, he bought a $37 million share in the Palazzo Grassi on Venice's Grand Canal; his art is now on display in the 18th-century white marble palace.