This point sits at a limestone ravine where the Atlantic pounds into a collapsed sea cave.
Last reviewed 4 October 2026 · A three-minute read · 3008 BC–1987
The short answer
Boca do Inferno is a sea chasm near Cascais, Portugal, formed when the roof of a sea cave collapsed, leaving the Atlantic to crash into an open limestone pit. It hosted one of the earliest films ever shot, in 1896, and in 1930 the occultist Aleister Crowley staged his death nearby.
Boca do Inferno, Cascais — 2006 · singra13 · CC BY-SA 3.0
1896 to 1930
A faked death and an early film both happened here
Boca do Inferno is a sea chasm on the rocky coast near Cascais, Portugal, now a popular lookout point. Its name means "Hell's Mouth." Waves rush into a deep gash in the cliffs and crash against the walls with a roar that gives the place its name. Historians credit the chasm's start to a sea cave. Its roof later fell in, leaving an open pit that the ocean still batters today.
In 1896, a filmmaker named Henry W. Short brought a camera to this spot. Short mounted it on a boat and floated it inside the cave. The result was a thirteen-second film of waves breaking at the cave's mouth. It became one of the first motion pictures ever shown to audiences, and people loved it.
In September 1930, the occultist Aleister Crowley arrived in Lisbon with a companion named Hanni Jaeger. Crowley left a note near Boca do Inferno suggesting he had thrown himself into the sea. The poet Fernando Pessoa helped spread the story to newspapers. Three weeks later, Crowley turned up alive at an art show in Berlin. A plaque near the rocks today still carries the words of his fake suicide note, translated into Portuguese.
Legend and limestone
A sorcerer's storm explains the name, or the cave's roar does
Visitors to the chasm often ask where the name came from, and two different answers exist side by side. One is a legend. The story goes that a sorcerer lived in a castle near Cascais and wanted to marry the most beautiful woman in the region. When she refused him, he locked her in a tower and set a guard over her. The guard fell in love with her instead, and the two fled together on horseback. The sorcerer, furious, called up a storm so violent it tore open the earth and swallowed the lovers and their horse into the sea. The ground never closed again. The legend holds that the horse's dying neigh carried all the way to a nearby beach, Praia do Guincho, and gave that beach its name.
Researchers who study Portuguese folklore give a different account. They argue the sorcerer story is a 20th-century invention, dreamed up after the cave's roof collapsed. They say the name "Boca do Inferno" is older than the legend, and describe it as naming the cave's dramatic, violent entrance from the water, back when it was still a sea cave used by local fishermen.
Before the cameras
A painter fixed the chasm on canvas before any camera
Before Short ever brought his camera here, the chasm had already caught the eye of painters. In the 1860s, the Portuguese artist João Cristino da Silva painted the formation, fixing it as a subject worth capturing on canvas decades before anyone thought to film it.
1930 to 1994
Storm-watchers and exiled aristocrats gathered at the same lookout
After Crowley's staged death faded from the headlines, Boca do Inferno kept drawing visitors for a simpler reason: the storms. Through the 1900s, people gathered along the cliffs just to watch the Atlantic throw itself into the gap, a habit that has lasted more than a century. In the early decades of the 20th century, European aristocrats fleeing wars and political upheaval settled in nearby Cascais, and many came to stand at this same lookout.
By 1981, the coastline around the chasm had been folded into protected land, and by 1994 that protection was formalized as the Sintra-Cascais Natural Park, covering roughly 145 square kilometers of coast between the two towns.
What's here now
The sea keeps widening the chasm it first carved
The chasm is still growing. The same erosion that opened it keeps widening it, year by year, as the sea works at the Cretaceous limestone. The plaque bearing Crowley's note still stands on the rocks, and the lookout remains one of the most visited points on this stretch of coast, especially when a storm is rolling in.
Waves still break into the collapsed cave, and the plaque with Crowley's fake suicide note still stands on the rocks above it.
Read the ground you are standing on
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Sourced records, high and medium confidence. Era background is marked as such.
Prehistoric
3008–2475 BC
Radiocarbon samples from a site about 1.3 kilometers from the chasm date human presence here to between 3008 and 2475 BC, the oldest dated trace in the area.
The Carmelite Convento de Nossa Senhora da Piedade, built in the late 1500s, was damaged in the 1755 earthquake and holds burials tied to its religious community before becoming summer homes in 1870 and a cultural center in 2000.
In 1896 Henry Short filmed the waves crashing through Boca do Inferno for 'A Sea Cave Near Lisbon,' one of cinema's earliest surviving actuality films.
In September 1930 the occultist Aleister Crowley left a suicide note at Boca do Inferno, with the poet Fernando Pessoa's help spreading word he had drowned, then turned up alive three weeks later at an exhibition in Berlin.
A white plaque fixed to the rocks here reproduces Crowley's faked farewell note in Portuguese: "I cannot live without you. The other Boca do Inferno won't be as hot as yours."
Prince Alfonso of Bourbon, youngest son of Prince Juan of Spain, died in 1956 at age fifteen while his family lived in exile nearby, and was first buried in Cascais.
What was here before Boca do Inferno became a lookout point?
The chasm began as a sea cave on the rocky coast near Cascais; its roof later collapsed, leaving the open pit the Atlantic still batters today.
Why is Boca do Inferno called Hell's Mouth?
Local legend tells of a sorcerer's storm tearing open the earth to swallow two fleeing lovers, but folklore researchers say the name is older than that story and simply described the cave's violent, roaring entrance from the water, used by local fishermen.
What happened at Boca do Inferno in 1930?
The occultist Aleister Crowley left a note near the chasm suggesting he had drowned himself there, a story the poet Fernando Pessoa helped spread to newspapers, before Crowley turned up alive three weeks later at an art show in Berlin.
Is there a film connection to Boca do Inferno?
Yes, in 1896 the filmmaker Henry W. Short floated a camera into the cave on a boat and produced a thirteen-second film of the waves, one of the earliest motion pictures shown to audiences.
Is Crowley's note still marked at the site?
A plaque fixed to the rocks near Boca do Inferno still carries the words of Crowley's faked farewell note, translated into Portuguese.
Where this came from
1
Atlas Obscura — Aleister Crowley faked his own death here
2
Wikipedia — One of the world's first films was shot in this cave
