The Gallery of Underground Wonders in Grotta Impossibile
Passage Thomas De Marchi - 2024-02
The cave Grotta Impossibile (Impossible Cave) is considered one of the "giants" of the Trieste Karst in the wider area around Basovizza. The first cave to earn this title was Grotta Claudio Skilan (Skilan Cave), and more recently, Sancinova jama (Sancin Cave), which is still awaiting further exploration.
The discovery of the cave in 2004, during the excavation of a tunnel for the Trieste bypass, was considered impossible, and many of the subsequent discoveries, which start in the large hall “Carlo Finocchiaro,” were equally incredible. The hall was discovered by cavers from the Trieste caving club C.G.E.B during early explorations, and later, through the long connecting meander “Ommagio al Chorchia,” they reached the branched northwestern sections. Eventually, they also reached the surface above the large hall, where they excavated a new entrance to the cave, as the original one from the highway tunnel had to be closed.
Exploration of the cave stalled in 2008 but never completely stopped. Most questions regarding possible continuations arose again in the large hall, as they searched for passages beneath its top, since most of the cave’s passages intersect at this height. The most promising area was above the well-known connecting passage “Passagio Venturi,” which required a 50-meter climb and the construction of several traverses. They reached a passage that soon turned in a different direction from the lower passage and ran parallel to the connecting meander.
Immediately upon entering the passage, we were strucked by its large dimensions and the beautiful speleothems of various shapes and color combinations. These formations can undoubtedly be ranked among the most beautiful in the entire cave. The old fossil passage, which drained water in ancient times, is relatively clean and free of sediments, but with fragile ground in many places, making it extremely delicate. It cannot withstand mass visits and requires great caution from cavers.
The passage is only interrupted by two narrowings, and after the second, visitors are surprised by a drill head and numerous PVC pipes, remnants of test drilling prior to the construction of the highway tunnel. During drilling, the workers unknowingly encountered an underground chamber, the drill dislodged, and the pipes broke like toothpicks on the cave floor. Cavers alerted authorities to the situation back in 2017 and even proposed a plan for removal, but institutions have yet to respond.
The main part of the passage increasingly ascends towards the end, culminating in a chamber with dried-up basins, beautifully concluding the roughly 400-meter-long gallery of underground wonders. The passage will surely remain well-preserved, as its access is strictly regulated by the caving club. The researchers named the passage after the tragically deceased Trieste caver and their friend Thomas De Marchi, who was deeply dedicated to the club’s work and cave explorations.
