by Alessandra Ressa
Speleologists have made a groundbreaking discovery beneath Italy’s Karst Plateau, uncovering hundreds of meters of previously uncharted galleries along the mysterious underground Timavo River. The find marks a major milestone in a decades-long exploration effort and could reshape our understanding of one of Europe’s most enigmatic underground water systems.
On March 23, 2024, after more than twenty years of relentless work, members of the Adriatic Speleological Society succeeded in navigating past the last set of obstacles within the Luftloch cave, revealing a new section of the subterranean Timavo River. The discovery adds a crucial third Italian cave to the network of known passages that intersect the river, following the Trebiciano cave, discovered in 1841, and the Lazzaro Jerko cave, which was first reached in 1999.
What sets this discovery apart is its scale. Speleologists descended more than 300 meters below the surface, entering a cavern of immense proportions. Using inflatable rafts to navigate the flooded passages, they explored an expanse of nearly 100 meters upstream, where they found a chamber dominated by a vast subterranean lake. Downstream, however, the explorers encountered an even greater surprise — a colossal gallery that stretches almost 100 meters before widening into a new passage, measuring 20 meters high and 20 meters wide.
“The sheer magnitude of what we’ve found is unprecedented,” said one of the lead speleologists. “We had to wait for the river’s summer low flow to safely navigate the gallery, which turned out to be twice as long as we had anticipated.”
The exploration of this hidden waterway represents the culmination of over 150 years of ongoing research. The first breakthrough came in 1841, when the Trebiciano cave was discovered during excavation efforts aimed at solving Trieste’s growing demand for water. While technical challenges at the time made it impossible to exploit the resource, the discovery of the Timavo ignited global interest in speleology, paving the way for organized underground exploration. It wasn’t until 1999, more than a century later, that speleologists uncovered a second link to the river through the Lazzaro Jerko cave in Monrupino.
The current discovery in Luftloch promises even more. Speleologists believe they are on the verge of uniting the newly discovered sections with Trebiciano. Underwater explorations conducted this summer in the older cave have already added another 300 meters of submerged paths, bringing the two caves within 200 meters of each other.
Connecting the two would create a single, continuous system tracing the underground course of the Timavo River for more than two kilometers — a monumental achievement for the field.
This latest find is part of the larger “Timavo System Exploration” research program, which aims to unravel the secrets of this elusive river. Originating in the mountains of Slovenia, the Timavo River plunges underground near the Italian border, only to reemerge 40 kilometers later on the Adriatic coast. For centuries, its underground route has baffled scientists and explorers alike.
Should the connection between the Trebiciano and Luftloch caves be established, it will provide unprecedented insight into the river’s subterranean journey, and offer new opportunities for research into hydrogeology, cave ecosystems, and the dynamics of underground rivers.
The Timavo has long held a mythical allure, with its hidden depths fueling both local legends and scientific curiosity. Thanks to this discovery, the Adriatic Speleological Society is now closer than ever to unveiling the full scope of this natural wonder.
