Boldt Castle

Boldt Castle on Heart Island near Alexandria Bay, New York, is a six-story castle in the middle of the St. Lawrence River. Hotelier George Boldt began building it in 1900 as a gift for his wife, Louise. When Louise died in 1904, he stopped the work and never returned to the island. The unfinished buildings then stood empty and exposed for more than 70 years. In 1977 the Thousand Islands Bridge Authority acquired the island and the Yacht House for one dollar, on the condition that the revenue go toward restoration.

Today the two lower floors are restored and furnished; exhibits on the region's history fill the upper floors, and the basement is largely unfinished. The site also includes the Power House and the lopsided Alster Tower. You can reach the island only by water: tour boats and ferries run from Alexandria Bay, Clayton, Gananoque, Rockport and Ivy Lea, among other places. The visitor season usually runs from mid-May to mid-October, so the island is normally closed in late fall (as of October 2026). Heart Island is a port of entry: if you arrive from Canada you are entering the United States and need valid identification.