A whispering gallery is usually constructed in the form of an ellipsoid, with an accessible point at each focus. When a visitor stands at one focus and whispers, the line of sound emanating from this focus reflects directly to the dish/focus at the other end of the room, and to the other person. Circular whispering galleries may provide "communication" from any part on the circumference to the diametrically-opposite point on the circumference.
Whispering galleries also occur naturally in the ocean. Instead of the reflecting surface it is the sound rays that are curved and the reflecting 'wall' (the sea surface) is flat. The same phenomenon occurs for radio waves propagating in the atmosphere.