Ask a Neapolitan where they go for a weekend: they say Ischia, not Capri. Capri is for tourists and day-trippers. Ischia is for people who want to soak in volcanic hot springs at sunset, hike to the summit of a 788m volcano (Monte Epomeo, 1.5h, the entire Bay of Naples beneath your feet), eat coniglio all'ischitana (rabbit slow-cooked in a clay pot with tomatoes and local herbs — the island's signature dish, €14), and float in thermal pools that have been heated by the same volcanic system since the Greeks discovered them in 770 BC. Ischia is 6x larger than Capri, has 6 municipalities, thermal gardens (Poseidon, Negombo, Castiglione — €30-40/day for pools ranging from 28°C to 40°C in gardens facing the sea), and hotels that cost 1/3 of Capri's prices. Ferry from Naples: €13-19, 60-90 min.
Plan my Ischia trip →Poseidon Gardens (Forio, €38/day): the most famous. 22 thermal pools at different temperatures, private beach, gardens descending to the sea. Crowded in August but magnificent.
Negombo (Lacco Ameno, €35/day): more design-conscious, Japanese-influenced gardens, art installations between the pools. Less crowded than Poseidon.
Sorgeto Bay (FREE): hot volcanic water bubbles into the sea at this rocky beach. You mix your own temperature by positioning between hot springs and cold sea. Access: 234 steps down from Panza village. Bring wine. Go at sunset.