Ischia is a volcanic island in the Tyrrhenian Sea. It lies at the northern end of the Gulf of Naples, about from the city of Naples. It is the largest of the Phlegrean Islands. Roughly trapezoidal, it measures approximately east to west and north to south and has about of coastline and a surface area of . It is almost entirely mountainous, the highest peak being Mount Epomeo at . The island has a population of over 60,000 people.