Ischia, a volcanic jewel in the Gulf of Naples with restorative geothermal waters, has lured travelers to its romantic, rocky shores since antiquity. The ancient Greeks and Roman emperors came to soak in the mineral-rich waters, pirate raids prompted the construction of the looming Aragonese Castle and 19th-century European aristocracy spent their summers under the Ischian sun (as well as famous creatives like W.H. Auden and Truman Capote). And unlike its busier neighbor, Capri, the island’s ter...