From the dentist office in the White House to the hidden room in Mount Rushmore, America's landmarks are full of secrets and awe-inspiring facts.
Yes, it's stunning, but the Gateway Arch is more than just looks: It also holds a fascinating piece of residential history at its very top. A time capsule was placed in the arch on October 28, 1965, and holds 762,000 signatures (many from students who attended St Louis schools at the time), according to the National Park Service. However, don't expect to see the list made public any time soon. The capsule is permanently welded inside the arch, and won't be opened as long as the structure is standing.