Stairway, Temple of Kukulcán, Chichén Itzá, Yucatán,

1932, printed later

Twice yearly, at sunset on the spring and fall equinoxes, crowds assemble at Chichén Itzá to watch Kukulcán, the feathered serpent god of the ancient Maya, descend to earth. The zigzag shadow that is cast along the pyramid’s north balustrade is suggestive of the pattern on a rattlesnake. Gilpin photographed the site during a chance visit in March 1932, years before the equinox shadow had been identified as an intentional architectural effect. Though most scholars agree that the shadow does reflect calculation by the Maya, the surface on which it occurs was reconstructed in the early twentieth century, incorporating stones that lay scattered at the site when it was discovered in 1839 as a steep jungle-grown ruin.