Boldt Castle is located in which country?

Boldt Castle is a major landmark and tourist attraction in the Thousand Islands region of the U.S. state of New York. Open to guests seasonally between mid-May and mid-October, it is located on Heart Island in the Saint Lawrence River. Heart Island is part of the Town of Alexandria, in Jefferson County. Originally a private mansion built for American millionaire George Boldt, it is now maintained by the Thousand Islands Bridge Authority as a tourist attraction.

George Boldt, proprietor of the Waldorf-Astoria Hotel in New York City and manager of the Bellevue-Stratford Hotel in Philadelphia, and his family enjoyed an earlier frame cottage on Hart Island (the island's original name) for several summers, which they greatly expanded. In 1900, George Boldt launched an ambitious construction campaign to build a huge masonry structure, one of the largest private homes in the United States. He engaged the architectural firm G. W. & W. D. Hewitt and hundreds of workers to build a six-story castle as a present to his wife. In addition, four other masonry structures on the island are architecturally notable.