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.

[10]: 8, 9  In 2004, caver Vlado Božić proposed that the entrance to the cave had been completely covered before this flood, which created the initial opening.

[11] This was dismissed by geologists Srećko Božičević and Mladen Garašić as a "fantasy",[12] but defended by geologist Hrvoje Malinar,[13] 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.

[2]: 2 In 1960, Božičević divided the cave into four sections: 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.

[16] 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.

[2][5]: 12 Systematic excavations began, led by Franjo Ivanček and Vladimir Mirosavljević, joined by Slavko Marjanac and Mirko Malez.

[5]: 13  Around the same time, Antun Markić began systematically photographing the cave,[5]: 13  the only previous attempts being those of Josip Poljak in his survey and of journalist Franjo Fuis published 20 April 1934 in Kulis.

[5]: 9  Concurrent with the archaeological and photographic documentation was an effort to map the entirety of the cave by Srećko Božičević and Slavko Marjanac,[5]: 13  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.

[1]: 13  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.

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.

These successes attracted some of the younger Željezničari,[f] who under the leadership of Božić discovered much of the so-called "New Veternica"[g] in 1964[h] (Kristalni kanal, Mlinarev rov, Velika dvorana).

Using those pitons, Svjetlan Hudec was able to climb a further 9 m up the same cliff on November 3rd, at the top of which was the largest chamber in the cave, named Markulinova dvorana.

[24] But some work was allowed to continue until a 2020 document[25] by the new rector Marina Popijač restricted the maximum caving time to 6 hours on 1 day of the month, making exploration trips impossible.

[24]: 85 The only notable steps towards exploration by cavers since the takeover were the 2009 laser telemetry of the main part of the cave from the entrance to the PVC siphon, providing greater vertical accuracy;[m] and the discovery of a new chimney inside Markulinova dvorana in 2012, alongside a few other minor passages.

The northern end of the Staglišče doline drains into the deeper parts of Vetrenica, which also receives water from the Ponikve polje.

[15]: 34  As the uplift continued, the mouth of the cave would have risen above the water level, leading to the formation of lower springs similar to Dubravica.

[15]: 36, 38 Much of the formation of Veternica formed in lacustrine conditions at least about 380 ka BP[14]: 218  at the unconformable contact between Miocene marly limestone and underlying Triassic dolostone,[26] as a largely phreatic subterranean paleolake 475 m upstream inside the cave.

[14]: 214  Sediment buildup blocking lower springs is proposed as the reason for the water level rise that allowed for phreatic conditions to dominate.

[14]: 215 Between about 245 and 235 ka BP, the system experienced a geologically rapid water level drop, as evidenced by the transition from shelfstone to flowstone.

[14]: 215  It has been suggested that this water table fall was due to the ~350 m tectonic uplift along the southern flanks of Medvednica in the Quaternary, which could also explain the recession of the main stream from the siphons Ponor 16 metara and Kukušni to Glavni.

[15]: 35–39 After hydrological activity ceased at the end of the Riss glaciation, the oldest clastic sediments at the cave entrance were deposited.

[29]: 48, 49 In 1956, the discovery of a human skull believed at the time to be around 150,000 years old was published, prompting a number of prominent anthropologists to visit Zagreb, including Hallam L. Movius, Germaine Henri-Martin, Ulrich Schaefer [de], Srečko Brodar, Božo Škerlj, Branko Gavela and others.

[44][16]: 67 Other invertebrates include Eukoenenia sp.,[16]: 67  Heteromurus nitidus Templeton, Lithobius sp.,[16]: 67  Mesoniscus graniger Frivaldsky,[45]: 244  Niphargus likanus Karaman,[42][46] Plusiocampa cf.

nivea Joseph,[16]: 67  Rhagidia sp.,[16]: 67  Schubartia lohmanderi Verhoeff,[42] Scoliopteryx libatrix L.,[16]: 67  Troglohyphantes excavatus Fage,[47] Troglophilus cavicola Kollar.

pristis Penard, Diplochlamys sp., Diplophrys sp., Euglypha bryophila Brown, E. laevis Ehrenberg, E. rotunda Wailes, E. tuberculata Dujardin, cf.

Flamella sp., Frenzelina sp., Heleopera sp., Korotnevella sp., Mayorella sp., Microchlamys patella Claparède & Lachmann, Microcometes paludosa Cienkowski, Plagiopyxis declivis Bonnet, Pyxidicula sp., Rhizamoeba sp., Tracheleuglypha dentata Deflandre, and Trinema lineare Penard, T. enchelys Ehrenberg, Vahlkampfia sp., Vanella sp.