Boldt Castle is a historic mansion located on Heart Island in the Thousand Islands region of the Saint Lawrence River, New York. Built in the early 1900s by hotel magnate George C. Boldt, the castle was intended as a tribute to his beloved wife, Louise. The construction was halted in 1904 after her untimely death, leaving the castle unfinished for many years. Today, Boldt Castle is a popular tourist attraction, showcasing its stunning architecture and beautiful gardens. It is part of the Thousand Islands National Park and is accessible by boat. The castle features numerous rooms, a grand ballroom, and a picturesque view of the surrounding river.