What is your favorite piece of under-appreciated or forgotten history? (Not your personal history)

I am always fascinated by the under-appreciated sides of well known events, forgotten events, and generally overlooked parts of history.<br><br>I think an excellent example of this is the 1904 NY World's fair, which featured a model of a utopian city on the moon with a self-sustaining oxygen supply and a 15 foot tall "astronaut" on top of one of the buildings to show that, with the technology of the time, a lunar colony would be feasible. <br><br>What is your favorite hidden history?