On the edge of a small cornfield near the ruined Maya city of Chichén Itzá, in the sparse shade of a tropical tree, a voice ricochets wildly up the mouth of a well. “¡Lo vi! ¡Lo vi!” the shout proclaims. “I saw it, I saw it!” “¡Sí, es verdad! Yes, it’s true!”
Leaning over the mouth of the well, underwater archaeologist Guillermo de Anda needs to make sure that this is what he has been longing to hear for so many months. “What is true, Arturo?” And his fellow archaeologist Arturo Montero, floating down at the bottom of the well, yells up again, “The zenith light! It really works! Get down here!” Then he whoops ecstatically.
What de Anda has been waiting anxiously for his friend Montero to determine is whether the water at the bottom of this nondescript natural well, or cenote, had acted as a sacred sundial and timekeeper for the ancient Maya on the two days of the year, May 23 and July 19, when the sun reaches its zenith. At that moment it is vertically overhead, and no shadow is cast. The fact that the cenote is directly northwest of the main staircase of El Castillo, the famous central pyramid of Chichén Itzá, and within that mysterious city’s urban limits, made de Anda’s question particularly intriguing.