Of the myriad memorials and places across the U.S. named for the first American president, the Washington Monument is the most iconic. The 555-foot obelisk attracts some 800,000 visitors each year, who come to admire the view from the tallest stone structure in the world.

What most onlookers don’t know is that the landmark pillar is hiding several secrets, quirks, and forgotten histories that are all too easy to miss without close inspection. Take a look at some of these fascinating stories you won’t get on the official tour.