Fort Niagara's Powder Magazine. Built by the French in 1757, it's one of the few original structures to survive the British siege of 1759, and was used to house the fort's ammunition until 1929!!

This structure may or may not have also played a part in the weird Morgan Affair. William Morgan, a bricklayer and mason from Virginia living in Batavia, New York in the 1820's, wrote a book that intended to reveal the secrets of the Freemasons. Many of America's Founding Fathers were Freemasons, as were many folks in authority in New York State at the time. For some reason, these secrets were so important that, before his book could be published, Mr. Morgan was arrested on trumped-up charges in 1826 and secreted from place to place. One of these places was reportedly Fort Niagara's Powder Magazine!

Morgan was either drowned in the Niagara River by the Freemasons or paid $500 to go away and never come back (depending on whose story one believes), and his book, when published posthumously, started a backlash against Freemasonry that ended with the world in flames. Not really, but it did make lots of folks unhappy with the Freemasons.