Price: $78 million
Location: Rollins, Mont.
Square footage: 24,000 (main house)
This castle-like Shelter Island Estate totaling 32,000 square feet of indoor space is located on the 24-acre Montana island of the same name in Flathead Lake, adjacent to Glacier National Park. Features of the property include a great room with 45-high ceilings and a second story gallery, a copper conservatory, and a windowed mahogany walk-in closet that's nicer than most people's homes. The mansion is crafted using Indiana and French limestone in numerous fireplaces, African mahogany, Italian plaster, copper and bronze.