In the 1970s, when the American government was preparing for the Bicentennial, officials discovered something totally wondrous at Lincoln Memorial. It turned out that Honest Abe was sitting atop a massive secret — literally. If you’ve ever set foot on the Tennessee pink marble floors and stared up at the stoic expression of America’s 16th president, you were standing right above a decades-old mystery.

A construction crew working at the Lincoln Memorial back in 1975 was tasked with renovating the bathrooms. However, not long into their project, they noticed something strange about the structure’s foundation that no one was prepared for.

Getty Images / Tzido