Above Cold Spring, New York, is the Bannerman Arsenal. The island was purchased by Francis Bannerman at the beginning of the 20th century as a summer residence and storage facility for his military surplus business. He built these structures as an advertisement to train and ferry travelers who could see the island on there way to or from New York City with the words "Bannerman Island Arsenal" printed on the north wall of the castle. Due to poor construction, decay, and an extensive fire in 1969, the island has been mostly derelict and left to fall apart. You can get here by seasonal tours, kayak/small boat travel... or you can see it by drone.