Železna jama

virtual excursion

Železna jama (The Iron Cave) lies on an isolated karst of the westernmost part of the Posavje Hills, in the wooded landscape above Gorjuša near Domžale. Although today it is arranged for tourist visits and welcomes visitors with a regular guiding service, its story is far older than human presence. Like all karst caves, the Iron Cave was shaped by water. Rainwater enriched with carbon dioxide seeped through cracks in the limestone, dissolving the rock and slowly widening the underground spaces. Its exact age cannot be determined, but the cave’s interior clearly bears the marks of millions of years of natural processes.

The temperature inside the cave changes throughout the year, but with a delay characteristic of massive rock. In summer, the cave is cooler than in winter, because the rock warms only after prolonged exposure to summer heat and releases that warmth months later. The origin of the name “Iron Cave” is not entirely clear. One explanation links it to the former extraction of iron ore in the area, supported by the remains of a smelting furnace with iron slag found nearby.

The original entrance shaft opens on the eastern slope of a sinkhole. The current artificial entrance tunnel, used by visitors today, was excavated in 1962 and 1963 when the cave was being prepared for tourism. On the western side, where the cave lies closest to the surface, an eight‑meter artificial entrance was created, while the original vertical chimney remained unchanged. The eastern wall, marked by the levels of an ancient underground stream, has preserved its original features. Along the main fracture, corrosion pockets and chimneys appear in succession, while several cracked rocks on the western wall had to be removed for safety reasons.

Železna jama consists of three chambers connected by a passage and bridges that form part of the tourist route. Inside the cave are numerous flutings carved by dripping water. A special feature of the cave are the curved stalactites, shaped by air currents during their formation—an unusual and intriguing speleothem form. The first and second main chambers are taller than they are wide or long, giving them the character of deep shafts. The first chamber narrows downward and transitions beneath the concrete path into a gallery barely a meter wide at the bottom. Because of its rich flowstone and stalagmites, it could be called the “Buried Hall”; beneath the ceiling stands a stalagmite more than a meter high.

The two chambers are connected by a short narrow passage with visible traces of former water flow on the ceiling and floor. At the bottom of both chambers, water sinks into the ground due to a clay threshold. The second chamber has a broader, artificially leveled floor, and its ceiling is smooth and rounded, as if sculpted by hand.

On the western wall, aggressive dripping water has carved small pockets and fluted channels resembling miniature karren. Because water seeps across the vertical wall, small calcite growths—tiny formations resembling hedgehog spines—develop. In the walls of both chambers are several steep fractures where rock blocks detached and settled due to internal pressures, adding geological dynamism to the cave.

The entire Železna jama is structured as a double shaft connected by galleries, deepened over time as the erosion base of the surrounding Gorjuša karst lowered. Present and ancient water flows penetrating through the ceiling are directed toward these two shafts. Although the cave is small, its micro‑forms are remarkably diverse: scallops, facets, corrosion pockets, remnants of cross‑sections of passages, rare stalagmites and stalactites, calcite growths, rimstone pools, small draperies, and the distinctive “cigar” formations. The cave is also notable for fractures caused by pressure release or stress on the walls of larger voids.

But Železna jamais not only a geological object for me. It was the first true karst cave with stalactites that I visited as a schoolboy nearly fifty years ago. At that time it seemed enormous, powerful, and mysterious—a place that transcended the everyday world and opened a doorway into the underground imagination. I remember the cool air, the smell of wet limestone, and the feeling of stepping into something ancient and unfathomable. That first encounter with the karst underground was a turning point that later shaped my interest in caves, the karst landscape, and the documentation of natural heritage.

I returned to the Železna jama also as a documentarian. I first documented it in 1998, when I began systematically recording Slovenian caves and karst phenomena. I returned again in 2007/2008, updating the visualization and illuminating its chambers anew—this time with the experience and technical refinement that come with time. Each return revealed new details, new shades of light, and new stories the cave tells through its stone.

Železna jama has thus become part of my personal and professional landscape—a cave that enchanted me as a child and accompanied me as an adult through work, exploration, and the documentation of Slovenian karst. It is a place where nature and memory meet, where science and experience intertwine, and a cave that still preserves its quiet yet powerful presence.