Use an acoustic anomaly to share a secret with a friend across a crowded station.

The perfect arch of Grand Central Terminal's Gustavino tile work allows for a very special acoustic effect known as a Whispering Gallery.

Grab an accomplice and head to the lower level of the Terminal near the Oyster Bar restaurant.

Stand across from one another underneath the walkway's arch, corner to corner. Press your ears up against the tiles and whisper your secrets through the walls.

Despite the crowds and noise of the station, your message will travel across the arch to reach your co-conspirator on the other side.