Ischia is a volcanic island in the Tyrrhenian Sea. It lies at the northern end of the Gulf of Naples, about 30 km from the city of Naples. It is the largest of the Phlegrean Islands. Roughly trapezoidal, it measures approximately 10 km east to west and 7 km north to south and has about 34 kilometres (21 mi) of coastline and a surface area of 46.3 square kilometres (17.9 sq mi). It is almost entirely mountainous, the highest peak being Mount Epomeo at 788 m.
The main industry is tourism, centering on thermal spas that cater mostly to European and Asian tourists eager to enjoy the fruits of the island's natural volcanic activity, its hot springs, and its volcanic mud.