Archaeologica.org

Ancient accounts suggest that Roman leaders Julius Caesar, Hannibal and Scipio Africanus worshipped at the Temple of Hercules Gaditanus, a religious sanctuary in what is now southern Spain. But the pilgrimage site’s exact location has long remained a mystery.

Now, researchers say they’ve discovered the ruins of that fabled temple—one of the “holy grails of archaeology,” according to Jesús A. Cañas of El País—in a shallow channel in the Bay of Cádiz. Using digital terrain modeling, the team detected a nearly 1,000-foot-long, 500-foot-wide structure that is only visible at low tide.