Bannerman Castle sits on Pollepel Island in the Hudson River near Beacon, New York, designed and built by Francis Bannerman VI as an arsenal. Described as a 'tiny jewel in the setting of the Hudson Highlands,' the structure is now preserved by the Bannerman Castle Trust, a nonprofit dedicated to its restoration. While the main building remains fragile and off-limits to enter, visitors can explore the island's extensive grounds, gardens, and trails via scenic boat cruises departing from Beacon, enjoying guided walks and historical lectures.