Pilis-nyergi Sinkhole

The Pilis-nyergi water sink cave was among the specially protected caves of Hungary. It is located in the Pilis Mountains in the Danube–Ipoly National Park. It also appears in tourist guidebooks.

Description

It is situated near the tourist route junction in the Pilis ridge. Its location is marked on some tourist maps. It functions as a periodic water sink. The cave passage, which can be traversed with basic equipment, may be visited only with a permit. It is currently not accessible because it has collapsed.

In 1967 the cave was first called Pilis-nyergi-víznyelőbarlang in the literature. In the literature the cave also appears under the names Pilisnyergi viznyelő (Bertalan 1976), Pilis-nyergi-viznyelő (Kordos 1977), Pilis-nyergi-víznyelő (Kordos 1984) and Pilisnyergi víznyelő (Horváth, H. Kelemen, Torma 1979).

Research history

The overview in the 1961 Karst and Cave Research publication mentions that the Kadić Ottokár Cave Research Group began dismantling the Pilis-nyergi water sink in 1961. The January–February 1962 issue of the Karst and Cave Research Bulletin notes that during the 1961 monastic research camp the dismantling work carried out in the periodic water sink in the Pilis ridge was done by one work group of the Kadić Ottokár Karst and Cave Research Department. The March issue of the journal reveals that a work group of the department was working in 1961 on the dismantling of the periodic water sink located in the Pilis ridge. The members built a protective, inflow dam in the periodic stream bed, then installed a winch on a three‑leg stand above the sink. The opened sink, moving among rubble stones, is vertical, about 6 m long and about 1 m in diameter. From there a side passage of about 4 m length and about a 20° slope was also made walkable, but the work was finished due to lack of time. In the shaft it is clearly visible that the stones are very eroded. A weak outward‑flowing draft could be sensed.

In 1964 the members of the group managed to explore the cave up to a length of 20 m, finding a small chamber at the end of the passage. According to the Pilis travel guide published in 1967, there is a water sink in the Pilis ridge between Nagy‑Szoplak and Fekete‑hegy, which was opened by Dorog speleologists. In the summer of 1964, at a depth of 15 m, the researchers entered the first small chamber of the Pilis‑ridge water‑sink cave, whose walls are decorated with beautiful dripstone encrustations and small dripstones. The continuation of the exploration work is encouraged by the strong airflow that began after the opening. In 1974 the Kadić Ottokár Speleology Group continued the work together with the Juventus Speleology Group, and increased the cave length by 4 m, which then was about 24 m. In 1974 the Foton Speleology Group prepared the photographic documentation of the cave.

In the book *Pilis útikalauz* published in 1974, in the list of caves of the Pilis Mountains and the Visegrád Mountains (pages 19–20), it is mentioned that between the caves of the Pilis Mountains and the Visegrád Mountains there is the Pilis-nyergi water sink cave. According to the section describing the caves of the Pilis Mountains, there is a water sink in the Pilis-nyereg lying between Nagy-Szoplak (the eastern part of the Pilis summit) and Fekete-hegy. In 1975 members of the Kadić Ottokár Cave Research Group carried out conservation and trail‑clearing work in it. In the manuscript *Magyarország barlangleltára* completed in 1976 it can be read that the Pilisnyergi water sink is located in the Pilis Mountains, in the Pilis range, at Kesztölc. It has an entrance in the Pilis-nyereg between Nagy-Szoplák and Fekete-hegy. The periodic water sink is 26 m long and 15 m deep. The part of the manuscript concerning the cave was written based on one literary work. In the list published in the 1976 MKBT Invitation it is mentioned that the Kadić Ottokár Cave Research Group, together with the Fényes Elek Cave Research Group, had a research permit in 1976 for the investigation of the Pilisnyergi water sink in the Pilis Mountains.

The Kadić Ottokár Cave Research Group and the Fényes Elek Cave Research Group descended to a depth of 34 m in the cave in 1976. At that time they carried out climatological measurements in the cavity system. In the 1976 MKBT Report, in a report written by Jánossy Dénes, it is mentioned that a scattered palaeontological find from the Pilisnyergi water sink in the Pilis Mountains emerged in 1976 (Lendvay Ákos). In the 1976 MKBT Report, in a report that came to light written by Kordos László, it is stated that Lendvay Ákos on October 10 1976 collected Equus caballus bones from the approximately 13–15 m deep, probably water‑logged sediment of the Pilis‑nyergi water sink. The approximately 40 m long cave was surveyed in 1977.

In the 1977 MKBT Report, in a report written by Kordos László, it is readable that Farkas Lajos (Dorog) found a horse tooth in the water‑logged sediment at a depth of 13–15 m in the water sink, which Lendvay Ákos handed over to the Hungarian State Institute of Geology on May 16 1977. In the book *Archaeological Topography of Komárom County* that appeared in 1979, it is mentioned that Benedek Anikó collected in 1962 from the bank of the Pilisnyergi water sink (site 18/8, Roman period, perhaps a village or settlement) in Pilisszentlélek a Roman‑period painted red pottery fragment, a large glass bottle base, late‑Roman grey granular dish fragments and a brick fragment decorated with a wave‑line pattern (Dorogi Coal Mine Regional Museum 62.15.1–7. The regional museum’s collection has been at the Balassa Bálint Museum in Esztergom since 1965). The publication contains a map of Pilisszentlélek on which the geographical location of the Pilis‑nyergi water‑sink cave can be observed. The site is marked with the number 8 on the map.