1 p.m. Bannerman Castle: The Medieval Ruins of Hudson Valley

For generations, boat and train passengers have been mystified by the sight of castle-like structures looming on an island in the Hudson River. Join Wes and Barbara Gottlock, authors of a book on the subject and tour guides of the island, as they detail the history of this remarkable site, dating back to 1900 when the land was purchased by Brooklyn resident Francis Bannerman (now buried at Green-Wood) for the storage of military goods which he sold through a world famous Civil War-era catalog. With extensive research and stunning photographs, the Gottlocks will cover the island’s rise as a glorious landmark and its eventual decline – plus the recent calls for preservation and restoration. Buy a book and have it signed, then board the Green-Wood trolley for a short tour, including a stop at the Bannerman family plot.