Slide 34 of 52: Standing guard over the Hudson River, some 60 miles (97km) north of New York City, is the abandoned Bannerman Castle. It's named after Scotsman Francis Bannerman VI, who owned a weaponry business and built this isolated island fortress in the early 1900s for use as an arsenal. Abandoned since the 1950s, the castle now stands in ruins, its turrets crumbling and greenery forcing its way through glassless windows. Still, it's a majestic site and a range of tours of the island are available.