Jonathan Blair/Corbis

Once the favored destination of Rome’s smart set, Baiae has gradually crumbled into the sea and now lies completely underwater. Thanks to recent advances in marine archaeology, however, many of its treasures have emerged from the deep. In this photo, a research ship conducts an excavation off the Baiae coast. Access to the sunken town is not restricted to archaeologists: Amateur divers also may explore the ruins, as author Tony Perrottet discovered to his delight.