9. Boldt Castle
In 1900, George C. Boldt, the proprietor of the Waldorf Astoria Hotel in New York, erected this 120-room castle for his wife, Louise, on an island in the St. Lawrence River in Alexandria, New York. Unfortunately, Louise died unexpectedly months before it was finished, so a heartbroken George halted building. It sat empty for 73 years until it was renovated and reopened in 1977 by the Thousand Islands Bridge Authority.
