Veternica is a cave located on Medvednica mountain in Zagreb, Croatia. At long, with a depth of and a vertical difference over , it is the longest known cave on its massif, and an estimated 6 km or more remain unexplored. In the 1960s, it briefly became the longest cave in Croatia. The first is available to visitors. In 2019, it had 5787 visitors. It is an archeological site where remains of several kinds of prehistoric animals as well as humans have been found. The cave has been protected by law since 7 July 1979, with registration as a Natural Monument on 11 July of that year.
Etymology The name Vetrenica is a Kajkavian -en-adjective formed from the reflex of Proto-Slavic větrъ "wind", to which the denominal suffix -ica has been added. It is named for the wind that comes from the lower entrance of a cave as a result of temperature differences, except in the winter. Specifically in caves with two or more entrances and a significant difference in elevation between them. The upper entrance in this case seems to be a pit cave discovered in 1973 and named Dvogača, which sucks in warm external air in summer but emits relatively warm internal air in winter, opposite of Vetrenica.
Description
Detailed descriptions of the cave itself can be found in Poljak 1934, Baučić 1945, Božičević 1960, Čepelak 1977, Čepelak 1979 and other sources.
The entrance is permanently dry, but Kramberger's guide relayed an account related to him by the father of his paternal uncle, the 60 year old Zolak Nacek, that Veternica had once flooded for 24 hours. In 2004, caver Vlado Božić proposed that the entrance to the cave had been completely covered before this flood, which created the initial opening. This was dismissed by geologists Srećko Božičević and Mladen Garašić as a "fantasy", but defended by geologist Hrvoje Malinar, who took Božić to evaluate the hypothesis in the cave on October 8th, finding multiple traces of an older flood in the main canal from the entrance to the stream, in addition to traces of high water level in the deeper parts of the cave where such levels had not been observed.
The wet part of the cave includes 14 active streams. Among other sources, these streams come from 9 known ponors, including 2 at Ponikve polje. The cave branches stretch towards these sinkholes, while the main channel runs 1250 m NNW towards Ponikve.
In 1960, Božičević divided the cave into four sections: The entrance itself with entrance chamber, in which the anthropological finds were made. The tourist section, ending 380 m from the entrance at Kalvarija, beyond which the original explorer Gršetić did not reach. Because this part and the first part of Majmunski prolaz formed underneath the level of the paleolake, in the phreatic zone, these passages are relatively wide and easy. Individual chambers are named, such as the Koncertna dvorana. The 1st branch from the entrance is the vadose Ponor 16 metara with 68.5 m of passage, carrying the cave to its deepest known point only 75 m above the elevation of the Dubravica spring. It is a potential path to reaching the current phreatic zone, whose source is the Glavni siphon and exit the Dubravica spring, but high CO2 concentrations of unknown persistence may create safety issues. The 2nd branch is the Velebitaški kanal with 730.5 m, opposite the Ponor 16 metara, mostly horizontal but with a deep vadose descent in the Velebitaški siphon. It extends towards the Družanica hill on the surface. The Velebitaški kanal is a narrow, canyon-type channel. The 3rd branch is the Separe appendix with 35 m. Within it is the chamber Trbušasta dvorana. Majmunski prolaz stretches from about 400 m to 900 m, exposed to geologically younger phenomena. It is narrower, with a gradually lower roof, and split into two levels at three discontinuous sections, the last of which is Ramzesovo šetalište-Pakao. The 4th/5th branch is the Pakleni kanal with 563.5 m, extending towards Družanica from the junction between Ramzesovo šetalište and Pakao. It is even more difficult to traverse than the Velebitski kanal, because in addition to the narrow and wet passages it abounds with drops. The 5th/4th branch is the Fosilna dvorana with the Kukušni vadose siphon, together with 88 m, entered at Pakao. It has a stream, and is a potential path to reaching the current phreatic zone. The 6th branch is the Kanal iznad Limunove dvorane with 85 m, extending towards Družanica, entered from a Pakao chamber known as Limunova dvorana. A mostly narrow but relatively horizontal passage, apart from the Bubrezi section. The hydrologically active section beyond that. Its main passage is the largest on average. The 7th branch is the Glavni siphon, which receives most of the water from the sections deeper in. The 8th branch is the Stari kanal with 85 m. It is wider and easier to pass. "New Veternica" with 453 m, a complex network of exceptional beauty as with Kristalni kanal and Dvorana kipova. It includes the Velika dvorana, one of the largest chambers in the cave, and the Kanal slapova with 9 waterfalls, though the tallest waterfall in New Veternica at 13 m is in the Vjetrova dvorana chamber. Alpinistički kanal with 531 m. Entered through the roof of the Tamna dvorana chamber, the 2nd largest chamber in the cave. It includes several chambers with abundant calcite decorations: Dvorana sa zidom, Lijepa dvorana, Kapelica. Aneks. Connects the Tamna dvorana to the Alpinistički kanal. Darijev kanal Begins with the Bijela dvorana chamber. The channel abounds with rhomboid calcite crystal formations. Kanal iznad Razrušene dvorane. Kanal iznad Visoke dvorane. Željezničarski kanal.
History
Discovery
The entrance to the cave was once only 45 cm wide and 29 cm high, requiring a prostrate entry; so unlike Velika peć na Rogu or the Pećina Svetog Marka, it was not mentioned in printed literature until the regional onset of speleology, beginning with the account of Dragutin Gorjanović-Kramberger in 1899. Word of the cave then spread with the works of .
An account of the first recorded entrance into the cave in February 1933 by Stanko Gršetić with his brother and father was published on 8 March 1934 in the newspaper Večer, which popularised the cave and in the resulting exploration frenzy, the more accessible parts of the cave were quickly stripped of speleothems and the walls covered in names and dates of early explorers, as a 12 November 1934 article in Večer complained. In reaction, the Društvo za poljepšavanje Stenjevca secured the entrance and began requiring an entrance fee.
Early exploration The first scientific exploration and mapping of the inside of the cave was made by and others in the spring of 1934, exploring the first 1488 m of passageway, as far as the Viktorija waterfall.
Entomologist Egon Pretner visited the cave in 1936, where he found the presence of Anophthalmus kaufmanni subsp. weingaertneri.
In the light of the Bombing of Zagreb, the Ministry of War of the Independent State of Croatia had ordered late in the year to explore the possibility of repurposing the cave as a storage shelter, but nothing came of it. In 1959, Hrvoje Malinar discovered 4 hand grenades and a German novel in Fraktur type, rheumatism oil and motorist or pilot goggles, all 1200 into the cave, evidently left by a German soldier.
Although not on the maps of the time, the cave had already been explored as far as the PVC siphon by 1945.
Resumed mapping
The cave entrance had become overgrown by 1947 when exploration resumed. The first geodetic map was drawn by a team of cavers in 1948, reaching as far as the PVC siphon and bringing the total length of the cave to just over 1590 m.
Apart from one shallow excavation by the Planinarsko društvo "Prijatelj prirode" in 1940, the cave had remained untouched by paleontologists since 1934, but in 1949 the Planinarsko društvo "Željezničar" widened the entrance and built paths for visitors of the first section of the cave, discovering alongside Roman coins and other Bronze to Iron Age artefacts the skeletal remains of five recent individuals, which archaeologist Franjo Ivanček speculated had been victims of Borčec-born marauder Mijo Brezović, who was folklorically associated with the cave.
In 1951, following years of continued devastation by speleothem-hunters, the Commission for Veternica was formed, fixing a gate to the entrance and standing guard on Sunday for several years following to permit entry to visitors who paid for entry, though the 1951 gate was destroyed in 1955, and the 1969 gate was destroyed in 1970.
Systematic excavations began, led by Franjo Ivanček and Vladimir Mirosavljević, joined by Slavko Marjanac and Mirko Malez. Around the same time, Antun Markić began systematically photographing the cave, the only previous attempts being those of Josip Poljak in his survey and of journalist Franjo Fuis published 20 April 1934 in Kulis. Concurrent with the archaeological and photographic documentation was an effort to map the entirety of the cave by Srećko Božičević and Slavko Marjanac, which by 1955 had barely progressed beyond the stream, including one expedition involving the first bivouac in the SR Croatia; it was finally finished as far as the PVC siphon at the end of 1959.
The cave was visited by French speleologist Norbert Casteret on 12 March 1955, expressing surprise that the cave had not yet been equipped with electric lighting for tourism. After receiving approval, the cavers of Planinarsko društvo "Zagreb", who had mostly transferred to the Planinarstvo društvo "Željezničar" and had begun visiting the cave almost weekly since 1950, built the first extensive paths for tourists under the leadership of professor Mirko Markulin.
In 1958, the Planinarsko Društvo "Javor" conducted a flow trace experiment at the Ponor Jezeranca, 900 m from the ponor in Veternica as the crow flies, and the fluorescein soon arrived in the Bijela dvorana of Veternica, flowing from there to the Glavni siphon and later to the Dubravica spring in the valley several hundred meters south of the entrance to Veternica. When the green dye appeared in Gornji Stenjevec, it unsettled the village, so that the trace organiser Tomica Imenšek had to spend the entire day drinking green water to show it was not toxic. A further tracer experiment was conducted under Srećko Božičević in 1969 with the same results, during which the dye took 8 hours to reach Veternica, indicating complex passages.
Further exploration For decades, the cave remained unknown beyond the PVC siphon, but the Glavni siphon remained the most intriguing siphon. Following an 3 m dive and then on 21 June 1959 an 8 m dive by Hrvoje Malinar with a Drâger Aqua-Lung to a sandy bottom (the first freshwater cave scuba dive in SR Croatia), continued exploration was not deemed worth the risk, but Malinar had detected a narrow opening. Even with improvements in equipment, a 1988 dive by Branko Jalžić was unsuccessful in progressing past the point reached by Malinar.
With the negative results of the dive and the remaining options for continuation growing increasingly difficult, the visits to the cave for exploration purposes by the original clubs decreased, and it became mostly a training cave for young cavers. One of their last notable contributions in this period came from Vlado Božić, who finished the map to the PVC siphon in the 1960s on the basis of the work done in the previous decade. Where the Željezničari left off, the Planinarsko društvo Sveučilišta "Velebit" began. In 1962—1967, the Velebitaši under Hrvoje Malinar discovered the Velebitaški kanal, Ponor 16 metara, Kanal iznad Limunove dvorane and the Kanal iznad Razrušene dvorane. These successes attracted some of the younger Željezničari, who under the leadership of Božić discovered much of the so-called "New Veternica" in 1964 (Kristalni kanal, Mlinarev rov, Velika dvorana). It was during this time that Drago Pavličević produced his series of photographs.