Su Sterru: The Sinkhole That Swallowed A Volcano 0 Comments

By Daniela Toti

On the vast Golgo Plateau, above Baunei in Ogliastra, the landscape appears gentle and peaceful.

Pastures, dark rocks, wind-shaped juniper trees, and the occasional pool of water reflecting the sky. No one would imagine that right there, in the heart of this plateau suspended between sea and mountains, lies one of the most impressive chasms in Europe.

Its name is Su Sterru, which in Sardinian means "the abyss" or "the cavity". And the first surprise is that it is not located inside a cave. It opens suddenly in the open air, like a wound in the earth.

For centuries, the shepherds of Baunei observed it without truly understanding it. They called it the Old Crater. Even old Italian topographic maps identified it as the remains of an ancient volcano. 

The theory seemed perfectly reasonable. But nature had prepared a surprise.

In July 1957, a group of Sardinian speleologists decided to descend to the bottom. Their first attempts failed: the ropes were too short. No one knew the true depth of the abyss. Finally, the young speleologist Umberto Pintori succeeded in reaching the bottom and solving a mystery that had endured for generations. Su Sterru was not the crater of a volcano. It was something far older.

After about twenty-six meters of basalt, the rock suddenly changes color. Black gives way to the pale white of Jurassic limestone. From there, the shaft plunges almost vertically for more than 260 meters, reaching a total depth of nearly 295 meters.

No ledges. No steps. No place to stop.

Just a continuous drop into the heart of the mountain.

The opening at the surface measures about twenty-five meters in diameter, but at the bottom the cavity widens to nearly forty meters, forming a gigantic underground chamber invisible from above.

Researchers eventually understood that the abyss had been carved slowly by water. For millions of years, rainwater eroded the limestone below. When the underground cavities became too large, the upper basalt "cap" collapsed, opening a karst shaft to the sky.

Today, Su Sterru is considered one of the most spectacular karst sinkholes in Europe and one of Ogliastra's greatest natural wonders.

But it is more than geology.

Standing at the edge of Su Sterru still evokes the same feeling experienced by shepherds centuries ago: the sudden awareness that a hidden world exists beneath your feet. A world of silence, darkness, and geological time. And perhaps that is its true magic.

Ancient legends still surround the abyss. According to local tradition, this was the lair of Su Scultone, a gigantic serpent that terrorized the inhabitants of the area and demanded the sacrifice of young maidens. The nightmare, legend says, ended when Saint Peter confronted the monster, seized it by the tail, and hurled it violently to the ground. The beast plunged into the depths of the earth, creating Su Sterru itself. Nearby, between the seventeenth and eighteenth centuries, a small church dedicated to Saint Peter was built.

Sardinia is famous throughout the world for its beaches, its wild mountains, and its ancient archaeological sites. Yet one of the island's most astonishing places is not found by looking toward the horizon.

It is found by looking down. Down into a hole in the earth that, for millions of years, has guarded one of the deepest secrets of Sardinia.

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Su Sterru is located in the territory of Baunei, in Ogliastra, about 13 km from the village. It can be easily reached by car and is one of the most fascinating stops to visit together with the Church of San Pietro al Golgo, Pedra Longa, and the famous beaches of the Gulf of Orosei.