Ricardo Belizón, a graduate student in southern Spain, was studying topographic maps of the Bay of Cádiz last year when he noticed an intriguing shape just off the coast. Under the waters of Caño de Sancti Petri, he noted a roughly 1,000 by 500-foot structure — and he believes it may be the lost Temple of Hercules. Long regarded as a "holy grail" for archaeologists, many ancient Greek and Roman leaders traveled to this site to pray for strength some two millennia ago.