Naszályi Sinkhole

Due to its geological value, the Naszályi-víznyelőbarlang is one of Hungary's specially protected caves. It is located in Vácon in the Danube–Ipoly National Park. It is one of the three specially protected caves of the Cserhát, and among them it is the deepest and longest. It is the ninth deepest cave in Hungary.

Description

It opens in the water sink of the narrow plateau located on the Naszály ridge, which has the largest water catchment area. This water sink is 100 metres long and 30 metres wide, with a maximum depth of 12–15 metres. It is situated about 700 metres northwest of the geodetic measuring tower. It formed in Triassic limestone. Stalactite formations and dissolved forms such as flowstones are found in it.

The sealed cave can be visited with the permission of the Danube–Ipoly National Park Directorate and the use of technical equipment. Because bats spend the winter there, the system cannot be entered in winter. It is the habitat of the country's largest colony of small long‑eared bats. True cave‑dwelling, i.e., troglobiont, organisms also live in its passages.

Narrow, collapsible passages, spacious chambers and steep sections alternate. The difficulty of traversing it is shown by the fact that about 700 metres of fixed rope had to be used to make this periodically waterfall‑obstructed and collapse‑prone cave more easily passable.

The names of the Cserhát specially protected caves begin with the letter “N”: the Naszályi-víznyelőbarlang, the Nézsai-víznyelőbarlang and the Nincskegyelem-aknabarlang. The name of the Cserhát's oldest known and most famous cave, the Násznép-barlang, also begins with the letter “N”.

The cave occurs in the literature under the names Great Sinkhole, Naszály Cave (Kordos 1977), Naszályi Szinlő-cave (Bertalan, Kordos, Országh 1976), Naszályi-water‑sink‑cave (Kordos 1978), Naszályi water‑sink cave (Bertalan 1976), Naszály Sinkhole‑cave (Takácsné, Eszterhás, Juhász, Kraus 1989), Naszály Sinkhole Cave (Takácsné, Eszterhás, Juhász, Kraus 1989), Naszály water‑sink cave (Dénes 1970), Sárkánygödri‑water‑sink (Thuróczy 1964), Dragon Hole (Tölgyesi 1974), Dragon‑hole‑water‑sink (Nyerges, Ézsiás 2003), Dragon‑hole‑water‑sink‑cave (Rónaki 2012), Szinkő‑cave (Kordos 1984), Szinlő‑cave (Dénes 1970), Szinlő cave (Bertalan 1976) and Színlő‑cave (Dénes 1970). In 1977 the cave was first called Naszályi‑water‑sink‑cave in the literature, in László Kordos’s publication.

Research history

In 1949 Tibor Gánti and László Bánhidi discovered the water sink. In 1952 the students of the Vác high school opened it by excavation under the direction of László Bánhidi and Tibor Joó. At that time it received the name Szinlő‑cave. Then it was known to be 120 metres long and 60 metres deep. In the book *Cserhát Travel Guide* published in 1957 it is written that near the Naszály ridge there is the recently discovered water‑sink cave. It is also mentioned in the book *Along the National Blue‑Tour Route* published in 1964.

In 1974, as a result of the joint work of the Central Cave Research Group of the Red Meteor Nature Lovers Association and the Victoria Cave Research Group, the passage system reached a depth of 165 metres. According to the status on 31 December 1975, the 60‑metre‑deep Naszályi‑water‑sink‑cave was the 35th deepest cave in Hungary. In 1976 the Naszályi Szinlő‑cave in Vác, located in the 5200 (Cserhát, Mátra) cave‑catalogue area, became a cave of national significance.

In the manuscript titled Hungary's Cave Registry, completed in 1976, it is written that the Naszályi water sink cave located in Vác on Naszály in the Cserhát Mountains has another name, Szinlő cave. At the top of the ridge between Naszály and Szarvas Hill, about 100 m ENE from the branching of the tourist trails, along a doline line, at the foot of a rock wall in a doline, is its entrance. The measured length of the cave is 130 m, the measured depth is 60 m. After further explorations its estimated length is 350 m, depth 120–150 m. It is an intermittent water sink formed along a tectonic fracture oriented ENE–WSW. Partially unexplored and dangerous. The part of the manuscript concerning the cave was written based on one literary work. After correcting the cave names in the list of caves of national significance compiled in 1976, the cave located on Naszály mountain in Vác appears in the list of caves of national significance compiled on May 30 1977 under the name Naszályi‑viznyelőbarlang.

From the article "The longest and deepest caves of Hungary (December 31, 1975)" published in the 1977 issue of Caves and Karst in English, it can be learned that the 60 m deep Naszály Cave (sinkhole) on Mount Naszály was the 35th deepest cave in Hungary on December 31 1975. The 33rd deepest cave (Róka‑hegyi‑cave), the 34th deepest cave (Papp Ferenc‑cave), the 36th deepest cave (Borókás‑cave No. 3 sinkhole) and the 37th deepest cave (Nagy‑sinkhole) are also 60 m deep. According to the situation on December 31 1977 (MKBH Invitation May 1978) the roughly 60 m deep Naszályi sinkhole on Mount Naszály is the 39th deepest cave in the country. According to the compilation published in the 1977 issue of Caves and Karst, on December 31 1977 the roughly 60 m deep Naszályi sinkhole, which existed in 1977, 1976 and 1975, is the 41st deepest cave in Hungary. The 42nd deepest cave (Bátori‑cave) is also about 60 m deep. This compilation is more up‑to‑date than the list published in the May 1978 MKBH Invitation.

The first half‑year issue of the 1980 Caves and Karst published that the prominent Naszályi sinkhole is located in the 5200 series of cave registry areas (Börzsöny Mountains, Cserhát Mountains, Mátra Mountains, Karancs Mountains). The cave’s registry number is 5221/1. The MKBH Documentation Committee will install at the site, as with the other prominent caves, the plaque bearing the cave’s registry number. The metal plate used for the registration number will be the same as the plates used for the other prominent caves.