Ischia geothermal spa parks are the island signature attraction, but Castiglione in Casamicciola, Negombo in Lacco Ameno, Poseidon Gardens in Forio and the free Baia di Sorgeto springs sit kilometres apart along the SS270 ring road. This planner sequences your chosen stops into a single-day loop and totals the 2026 entry fees, parking, drive times and fuel. Castiglione opens at 10:00 with free parking and a standard adult day around EUR 33. Negombo is the priciest at EUR 55 in shoulder season and EUR 70 in July and August, with an EUR 8 lot that includes an EV charger. Poseidon, the largest park, costs EUR 40 to EUR 47 by season plus a refundable EUR 5 cash wristband deposit and EUR 6 parking that is free on weekdays in May and October. Baia di Sorgeto is a free natural cove where vents reach 90 to 95 C, reached by 230 to 250 steep steps. Sant Angelo is a car-free village where you park at Cava Grado and walk in. The SS270 is a single two-lane ring of about 34 to 40 km; drive times roughly double in July and August and the Porto, Forio and Casamicciola lots fill by 09:00. The historic centres of Ischia Porto and Forio are camera-enforced ZTL zones with fines of EUR 83 to EUR 332, so keep the car on the ring and in the spa lots. Most visitors do best pairing one paid park with the free Sorgeto springs, budgeting roughly EUR 45 to EUR 60 per person. The EAV bus reaches every park on a EUR 5.10 day pass, but a compact rental wins once you want two or more stops in a day.