18. Oheka Castle
Oheka Castle, built for the capitalist Otto Hermann Kahn, is a massive estate on the North Bank of Long Island, New York. The name Oheka is taken from an acronym for Kahn's name and is also used to name at least one of the yachts and a second house, Villa Oheka, in Palm Beach, Florida.
The villa was built from 1914 to 1919 and is the second-largest private house in the whole United States; it has 127 giant rooms and more than 109,000 square feet of floor space. Oheka Castle is currently operated as a historic private rental hotel, event planning, filming, and more.
