Fort Ticonderoga, New York - Ethan Allen and the Green Mountain Boys, along with Benedict Arnold, captured the fort on May 10, 1775. The capture stalled a planned British invasion from Canada and also enabled American troops to invade Canada themselves. The British recaptured the fort in 1777 but abandoned it in 1780.
Great Wall of India– The Kumbalgarh Fort. This is the second largest continuous wall on the whole planet. There are 360 Hindu Temples within the fort complex, along with the Maharaja's Grand Palace, Yet bewilderingly, it is still little known outside of India!
Abandoned Florida Fort Jefferson; Work began on this fascinating, unfinished coastal fort in 1846 and the building is still the largest masonry structure in the Western Hemisphere, comprising of over 16 million bricks. part of Dry Tortugas National Park and can only be reached by seaplane or boat.