A "whispering gallery" (WG) at the Great Ballcourt (GBC) was first reported during its excavation in the 1920s by American archaeologist Silvanus Morley (1883-1948), Director of the Carnegie Institution's Chichen Itza project. In his 1925 National Geographic article Morley wrote: "Standing in this temple one can speak in a low voice & be heard distinctly at the other end of the court, 500 ft away." Around 2000-2001, queries on AZTLAN, a semi-official Mesoamerican archaeology Internet discussion group, found little or no belief in a WG by mesoamericanists. Some opined that any WG would surely be a design accident or an artifact of ballcourt ageing or reconstruction. They stiffened at the suggestion that the ancient Maya might have possessed the requisite knowledge for intentional design. Was Morley mistaken? Or are modern mesoamericanists missing something? During a tour of Chichen Itza following the fall 2002 joint acoustical meeting in Cancun, Mexico, the author and two of his colleagues convincingly demonstrated a GBC WG to about 100 acousticians and their companions. This paper describes WG phenomena observed at the Great Ballcourt and suggests physical models to explain them. He also presents evidence for intentional design.