This is El Castillo, the 1,100-year-old Mayan pyramid on Mexico’s Yucatán Peninsula. It’s long been known that if you stand at the base of the staircase and clap your hands, the pyramid will return a “chirped echo” — a curious “chir-roop” with a characteristic lilt.

In 2002, on a hunch, acoustical engineer David Lubman compared the echo with a Cornell recording of the quetzal bird, which was revered in ancient Mesoamerica.

They matched perfectly.