Lonely Planet review for Solfatara Crater
Unnerving and surreal, this steamy crater was called Foro Vulcani (home of the god of fire) by the Romans. At the far end of the crater you can see the Stufe, two ancient grottos excavated at the end of the 19th century to create two brick sudatoria (sweat rooms). Christened Purgatory and Hell, they both reach temperatures of up to 90°C.
The crater's acrid steam, bubbling mud and sulphurous water have been lauded for their curative qualities for thousands of years. If the thought of reaching the crater on foot sounds like purgatory, catch any city bus heading uphill from Pozzuoli metro station and ask the driver to let you off at Solfatara.