Boca do Inferno - Devil’s Mouth

Cascais Municipality, Portugal, Portugal

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Boca do Inferno, or Devil’s Mouth, is a dramatic natural chasm carved into the seaside limestone cliffs northwest of Cascais in Portugal’s Lisbon District, where powerful Atlantic waves crash violently into its depths, creating explosive sprays and thunderous roars that earned its hellish name.

Formed by erosion from acidic rainwater weakening a limestone vein to collapse a sea cave into an open archway and cavern, it’s especially spectacular during winter storms when water erupts like a geyser, though it remains a year-round draw for its raw coastal power.

Just a short walk from Cascais center, the free site features a viewing platform, nearby seafood restaurant, handicraft market, and a curious 1930s tale of occultist Aleister Crowley faking his death there in a publicity stunt. Notably featured in the 1896 film A Sea Cave Near Lisbon—one of the earliest moving pictures—it captivates visitors with stunning sunsets, rugged paths, and the ocean’s unrelenting force.