Bocca Grande

Bocca Grande — 'Big Mouth' — is a natural volcanic vent or thermal spring outlet in Italy, likely in the volcanic zone of the Phlegraean Fields (Campi Flegrei) near Naples or in the volcanic Lazio landscape around Viterbo, where sulphurous water and volcanic gases emerge powerfully from the earth at this major geothermal expression point. The Phlegraean Fields, the world's only confirmed active 'supervolcanic caldera' beneath a major metropolitan area, contain numerous bocche (vents) of varying intensity, and the tradition of using these volcanic emissions for thermal bathing and inhalation therapy dates back to ancient Greek and Roman civilisation. The extraordinary geological drama of volcanic Italy — from Vesuvius to Stromboli — gives sites like Bocca Grande an elemental geological character unmatched in western Europe.