The first train to ever pull into St. Louis’ Union Station did so on September 2, 1894. The last departed on October 31, 1978. For many years in between it was one of the busiest train stations in the world. The Whispering Arch was there through it all and still remains.

According to legend, the Whispering Arch was discovered during the building’s construction in 1890. One builder dropped a hammer, and another heard it—nearly 40 feet away. The phenomenon is like that in the whispering gallery of St. Paul’s Cathedral in London: Essentially, a vault has been constructed in such a way that sound waves cling to and travel around its curve, popping up at either end of a concave surface.

The Whispering Arch is easy to find. It’s surrounded by beautiful, restored green and gold detailing and frames a stained Tiffany glass window featuring three robed women figures. The women, clad in yellow, red, and green, also date from the station’s earliest days, and represent the largest and busiest train stations of the 1890s: New York, St. Louis, and San Francisco. At its peak, 22 railroads connected through St. Louis, dwarfing any other station in the United States. By 1940, 100,00o passengers were passing through its vaulted Grand Hall every day. 

For the trick to work best, two people should stand in opposite corners of the gallery, facing the wall. One should whisper, and the other should listen. The sound will come through loud and clear, as it has for over 100 years.