Spluga della Preta: one of the deepest abysses on the planet is located in Italy, but how deep is it?

The Spluga della Preta is a karst cavity located in the municipality of Sant’Anna d’Alfaedo, north of the summit of the Corno d’Aquilio. The entrance is located in the pialde area, an offshoot of the province of Verona which extends into that of Trento, and reaches a depth of 877 metres, and is one of the deepest natural cavities in the world.

We are talking about an impressive abyss, which suddenly opens up among the green mountain pastures at an altitude of around 1500 metres, a place as fascinating as it is dangerous, which has attracted the attention of hikers and speleologists for almost a century.

The name, “Spluga della Preta”, literally means “cave that opens into the pasture”, a direct reference to the surrounding landscape, where it is not uncommon to find cows grazing near the fence surrounding the chasm. Despite the apparent tranquility of the surrounding environment, the cave hides an incredible depth: the first well, which alone measures 131 metres, is followed by two other consecutive wells of 88 and 108 metres. Overall, the Spluga extends almost 900 meters deep, an underground labyrinth that has intrigued and intrigued explorers and scholars since the early years of the twentieth century.

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The first explorations and the charm of the challenge

The history of the explorations of the Spluga della Preta officially begins in 1925, when a group of speleologists descended the first well for the first time. Interest in the cave grew rapidly, also thanks to the fact that during the fascist regime Italy tried to establish itself as home to the deepest cavities in the world. In 1927, an Italian expedition reached the altitude of -400 meters, although at the time a goal of -627 meters was declared, to increase national prestige.

As time passed, interest in Spluga continued to grow, in the 1950s new expeditions explored further meanders and wells, increasing knowledge of this impressive cave and taking speleologists to ever greater depths. The expeditions, often numerous, were real tours de force, with heavy equipment that was difficult to transport: the rope ladders used to descend into the wells were assembled manually, and each descent was a physical and mental undertaking. As exploration increased, a further problem also emerged, consisting of an incessant accumulation of waste.

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The record for the deepest abyss on Earth

For many years considered the deepest natural abyss in the world, the Spluga della Preta was renamed the “Benito Mussolini Abyss”, an erroneous record that lasted for 26 years.

On July 10, 1963, explorers reached the bottom of the so-called “Black Hall” at 875 meters, believing it to be the deepest point of the abyss for the next 18 years. This feat made the Spluga della Preta the deepest abyss in Italy and the second deepest in the world. During this exploration, at 510 meters deep, a rare troglobite beetle was discovered, the Italaphaenops dimaioi Ghidini, belonging to an unpublished genus and species.

In December 1981, a joint expedition of the Speleological Groups of the CAI of Verona, Vittorio Veneto and the Sacile Caves Group identified a “window” in the vault of the Black Room, which led to a vertical branch of about 100 metres. This passage allowed the speleologists to reach the “Fondo Nuovo” of the abyss. It was initially thought to be at a depth of 985 metres, but later topographic surveys established the true depth at 877 metres, with the bottom of the Black Hall located at 777 metres.

The waste problem

From 1925 until the 1980s, each expedition left behind traces of its passage: organic waste, bottles, cans, shreds of fabric and even broken or unusable speleological equipment. These materials, abandoned in hidden ravines or left at the bottom of the cave, became an integral part of the underground landscape, and Spluga, while remaining a place of scientific and sporting exploration, began to accumulate worrying quantities of dirt.

It was precisely in this context that Operation Corno D’Aquilio (OCA) came to life in 1988, a project that forever changed the relationship between speleologists and the underground environment. The idea behind the operation, promoted by Giuseppe Troncon, was simple and revolutionary: bring the waste accumulated over the years to the surface. Until that moment, many had suggested hiding the waste in the lateral branches of the cave or even burning it, while Troncon’s project envisaged its total removal.

The reclamation of the Spluga

Operation Corno D’Aquilio represented a real turning point in the history of Italian speleology, from 1988 to 1993, over two hundred speleologists from all over the world took turns to reclaim the Spluga della Preta. Each speleologist who participated in the operation found himself having to climb up the shafts with bags of packaged waste, carrying them along the tortuous meanders of the cave. The undertaking required thousands of hours of work and, in the end, four tons of waste were removed from the cavity.

The success of the operation was not only logistical, given that thanks to the reclamation of the Spluga, a new way of experiencing speleology was established, based on greater environmental awareness: for the first time the cave was no longer seen only as a place to explore and study, but also as an ecosystem to be protected and preserved.

The rebirth of the Spluga della Preta

With the conclusion of Operation Corno D’Aquilio, the Spluga della Preta returned to shine, free from the waste that had suffocated it for decades. The feat became a symbol for the entire speleological community, representing a great victory for the environment and a model of international collaboration.

In 2005 the documentary film L’Abisso was released, written by Francesco Sauro and directed by Alessandro Anderloni, which recounts the explorations at Spluga della Preta and achieved great success. The cavity, the protagonist of the film, became a sort of “actress” in the international speleological panorama, arousing even more interest among explorers and scholars.

In 2011, thanks to the publication of the volume La Spluga della Preta, which recounts twenty-five years of research and exploration from the Corno d’Aquilio Operation to today, the value of the enterprise was further consolidated, telling the history of the reclamation and the evolution of speleology in the following years.

A place of fascination and danger

Today, the Spluga della Preta continues to fascinate speleologists and mountain lovers, but it remains an extremely dangerous place. The perimeter of the cave is fenced to prevent people or animals from falling inside, and experts always recommend maintaining a safe distance, and it is also forbidden to throw objects into the chasm or fly over it with drones, as there could be speleologists in exploration.

However, Spluga remains an attraction for many hikers who, starting from the Tommasi district, reach the cave following various trekking routes. Anyone wishing to venture into these areas should be aware of the need for suitable equipment, mountain shoes and weatherproof clothing, as weather conditions can change rapidly.

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