Sixteen hundred years ago, the inhabitants of the powerful ancient Maya kingdom of Tikal looked to the west and saw red. On a hilltop, in their direct line of sight, stood the Temple of the Night Sun.

Choked by rainforest and crowded with fallen leaves, palms, and chunks of stone, the little-known site of Chochkitam, Guatemala, seems an unlikely place for a breathtaking archaeological find—much ...