For generations, boaters and train passengers have been mystified and intrigued by the sight of a castlelike structure looming in the Hudson River, near Fishkill. Bannerman Castle unveils the history of this site: an island arsenal, built to resemble a Scottish castle. The story begins in 1900, when Francis Bannerman VI purchased the island--officially Pollepel but later called Bannerman's Island--for storing used military goods purchased from the government. A native of Scotland, Bannerman designed his arsenal to resemble a Scottish castle.