Ürömi Sinkhole

The Ürömi water well cave is one of Hungary's specially protected caves. It is located in the Pilis Mountains within the Danube–Ipoly National Park. In the Budapest area it is the only water well that operates periodically. The cave is also described in tourist guidebooks. Antal Koch mentioned the water well in writing as early as 1870.

Description

In the inner area of Üröm, proceeding from the centre of the settlement, on the left side of Kőbánya Street, it opens in a bushy, approximately 10‑metre‑deep depression. A relatively long, intermittently flowing water stream leads to the cave entrance at the bottom of the water well. When the water flow increases, for example during snow melt or heavy rain, the water in the well swells because the well cannot immediately discharge the water.

The complex, multi‑level passage system formed in Eocene, nummulitic limestone. Its horizontal extent is 44 metres. There are also places where eight different level cave passages intersect each other at a single point in the plan. Many narrow, difficult‑to‑traverse squeezes occur inside, such as the Attila squeeze forming the entrance and the Beszterczey squeeze. Because of the proximity of the inhabited area it is polluted with waste. It is the only periodically operating water well in the Budapest area. One of the deepest points of the cave is the Szabó József chamber, named after Szabó József. Access to the cave requires a permit from the Danube–Ipoly National Park Directorate and basic caving equipment.

It is one of the three specially protected caves of Üröm, the other two being the Amphitheatre Cave and the Róka‑hegy Cave.

In 1958 it was first called the Ürömi sinkhole cave in the literature. The cave appears in the literature under the names Farkasverem (Koch 1871), Rókahegyi víznyelő (Kordos 1984), Rókahegyi viznyelő (Bertalan 1976), Üröm Cave (Kordos 1977), Ürömi viznyelő (Kadić 1952), Ürömi-viznyelőbarlang (Kordos 1978), Ürömi viznyelő barlang (Bertalan 1976), Ürömi-víznyelő-barlang (Gyurkó 1993) and Wolfsgrube (Koch 1871).

Research history

In the 1870 Natural Science Gazette Antal Koch mentioned the Ürömi sinkhole. According to Antal Koch's study published in 1871, Farkasverem and Wolfsgrube are the names of the sinkhole, and Antal Koch assumed that the sinkhole continues in a cave. In his 1914 work published in *Barlangkutatás*, Imre Gábor Bekey also mentioned the Ürömi sinkhole cave. The publication states that there are three sinkhole caves in the Pilis Mountains: the one near Üröm, which is located under Róka Hill, the Cat Cave, and the one opening in the Szurdok of Pilisszentkereszt. In the compilation *The Caves of the Pilis Mountains* published in 1937 it is written that the cave had not yet been found. In the 1940 journal *Magyar Katonai Szemle* Ferenc Hampel published the description *The Ürömi sinkhole (ponor)*.

In the 1940s Bertalan Károly and Imre Hluchányi, as well as the TTE speleologists, carried out exploratory work at the cave, but unsuccessfully. The 1948 Hydrological Gazette mentions that the stream of the Üröm sinkhole in the Transdanubian Central Mountains is intermittent. In 1950 Leél-Őssy Sándor and his companions succeeded in entering the water-draining cave. In April 1950, with the support of the Institute of Geology, the entire currently known passage of the cave was discovered. They wanted to reach the level of the karst water, but this was not achieved. In that year Leél-Őssy Sándor produced four plan maps of the cave, a longitudinal section map of the upper part of the cave and a plan map of the Üröm water drains.

The book Pilis guidebook, which appeared in 1955, states that it is the latest discovered cave in the region. It is located about 300 m from the eastern edge of Üröm, at the bottom of a non‑draining, closed, deep depression that is clearly visible from a distance. The cave is about 25 m long. The cave’s water drain is very interesting, because precipitation flows very quickly down through two small fissures at the bottom of the approximately 10 m deep and about 30 m wide depression. The passages did not form on a single level, but are situated one below the other, forming several levels that branch out. Several‑metre‑high vertical shafts connect the levels. The sections called Kutyaszorító and Névtelen szorító are very narrow. The cave contains two large chambers. At the committee meeting of the Hungarian Hydrological Society Karst‑Hydrological and Speleological Committee held on 12 January 1956, it was stated that, according to the final announcement and coordination of work areas, the task of the ELTE Department of Geography Karst and Speleology Group is to re‑explore the water drain.

The 1958 Geographical Bulletin mentions that there are upper Eocene bryozoan marl spots at the water well located on the K side of the Üröm basin. There are water wells in the Kevély hill group, but except for the Üröm water well they are small and rarely operate. The Üröm water well is located about 300 m from the K side of Üröm. It is the only active water well in the Budapest area. About 0.8 km² of catchment area belongs to the water well and two short intermittent streams flow into it. The Üröm water well is a covered karst phenomenon because its entrance was formed in bryozoan marl, which here forms a cover layer about 10 m thick. The water‑well cave located under the water well lies in nummulitic limestone. The water well operates only periodically and for a short time, during thaws and after heavy showers. It was created in a tectonic fault and has two openings that are situated side by side. In 1950, the karst research group of the University Department of Geography uncovered a large active water‑well cave under the water well, led by Sándor Leél‑Őssy. The study titled The Üröm Water‑Well Cave deals with the water‑well cave in detail and was published in the 1952 volume of the Hydrological Gazette.