An official Path Through History Site! This 120-room Rhineland-style castle and yacht house are one of the Thousand Islands' top attractions. In 1900, millionaire George Boldt commissioned a six-story castle for his wife, Louise. When Louise passed in 1904, Boldt was too heartbroken to continue construction. In the 1970s, the Thousand Islands Bridge Authority restored and completed the castle, now accessible to visitors by tour boat, water taxi, and private watercraft. Boldt Castle is located in the US, so passengers arriving by boat from Canada must provide proper identification for US Customs and Border Protection clearance.