Karolina Hole

The Karolina-cave is one of the cavities located in the Karolina trench in the Visegrád Mountains of the Danube–Ipoly National Park, in Pomáz. It is also mentioned in tourist guidebooks.

Description

In the Karolina trench, 200 metres from the intrusion of the Karolina trenches into the Holdvilág trench, 8 metres west of the lower subcave of the Karolina trench, higher, 8 metres above the valley floor, and almost parallel to the valley line, there is a rock wall 5–6 m high and 20–25 m long, containing smaller blocks, composed of andesite conglomerate. The Karolina-cave is recessed into the base of this rock wall.

One can reach it either by walking along the slope on the right side of the valley, or by dangerous rock climbing up the side wall of the lower subcave of the Karolina trench.

The cavity has a low, 50–70 centimetre high and 8 metre wide mouth facing southeast toward the Karolina trench. At the southern part of the entrance, a stone ledge 3.5 metres long rises up to the half‑height of the opening. Behind the wide entrance the cavity’s chamber is also wide, and its length is only a fraction of that. The chamber’s total width is 11.7 metres and its length is 4.5 metres. At the entrance the low ceiling gradually rises inward to 2–2.2 metres. Its side walls are made of layered andesite conglomerate, and its top is also formed by a conglomerate slab that rises along a fracture parallel to the entrance line. The floor is leveled, flat, and consists of broken debris.

The cavity was formed by lateral erosion when water still flowed at a higher level. Then, as the valley was cut deeper, the cavity became completely dry.

The cavity is an ideal bivouac site for 8–10 people. This feature is even utilized, as evidenced by climbing marks on the walls and firewood, glass bottles, and canned food cans left at the bottom.

In 1984 the cavity was first called Karolina in the literature. The cavity also occurs in the literature under the names Karolina-odu (Ozoray 1960), Meleg-fészek (Ozoray 1963) and Melegfészek (Ozoray 1960).

Research history

The 1960 Karst and Cave Research Bulletin states that the Warm Nest stone niche in the Karolina branch of the Moonlight Trench is a cavity cut by lateral erosion, which is often used by tourists as a night shelter. According to the study published in the 1963 Karst and Cave by György Ozoray, there are several insignificant‑sized but morphologically and origin‑wise interesting non‑karst cavities in the Karolina trench. On the convex side of a small sudden bend of the Karolina trench is a rock wall 5–6 metres high, at the foot of which the cave opens. Tourists know it well and often use it as a sleeping place. It is 8 metres wide, 4 metres deep, i.e., long, and 1–2 metres high. Its top is almost flat, lowering in the southern part and higher in the northern part. In the middle a vertical north–south rock slab can be seen. Such rock slabs may also have contributed to the formation of the vertical rock wall.

The cavity's filling rock is andesite conglomerate, but denser and finer than the higher part of the rock wall. Perfectly a settlement with a floor. On the north side of the cave there is a small, collapsed niche, which is divided by a re‑prepared, denser rock slab. Its floor is hollowed out, almost leveled debris. An artificially placed stone chain and earth chain narrow its entrance. On the convex side of the bend a rock cavity carved by lateral erosion. Periodic water flow eroded the rock wall, from which it was reflected in a broken arc. The water then continued down the lower sub‑cave waterfall of the Karolina trench. After the stream descended further, the cavity was further enlarged by chemical and physical collapse forces. The ceiling rose up to a stable conglomerate slab by collapse. The collapsed blocks were carried out by people and placed on top of each other at the entrance to make a more comfortable shelter. The publication includes the cavity's plan map with three cross‑sections, as well as a cross‑section shown on the cut‑map of the lower sub‑cave of the Karolina trench and the surrounding area. The maps were made by Fodor Tamásné and Ozoray György.

The book Pilis útikalauz published in 1967 states that at the base of the vertically descending steps of the Karolina trench there are small cavities, which are filled with collapse debris in a cave‑like manner. The Pilis útikalauz published in 1974, in the list of caves of the Pilis Mountains and the Visegrád Mountains (pages 19–20), mentions that the cavities of the Karolina trench are located between the caves of the Pilis Mountains and the Visegrád Mountains. In the section describing the caves of the Visegrád Mountains the description mentioned in the 1967 guidebook is repeated.

In the manuscript titled *Hungary's Caves*, completed in 1976 and written by Bertalan Károly, it is written that the Karolina-odu, also known as Melegfészek, is located in the Visegrád Mountains, Pomáz, in the Karolina branch of the Holdvilág trench, above the seasonal waterfall, on the right, north side of the valley. Its entrance is about 4 m wide, 1 m high, and artificially narrowed with a stone sill and a earth sill. On the curved side carved by lateral erosion, there is a 4 m long, 8 m wide and 1–2 m high rock cavity. Tourists often use it as night accommodation. The part of the manuscript describing the cavity was written based on three literary works.

The 1980 MKBT Report published the 1980 report of the Békásmegyer Cave Research Group, which states that a Christ monogram (the Greek initials of the name Christ) is found inside a naturally formed cave on the left side of the Karolina trench. In the 1984 book *Caves of Hungary*, the national cave list includes the cavity under the name Karolina-odu with the variant Melegfészek among the caves of the Szentendre–Visegrád Mountains. Associated with the list, the geographic location of the Dunazug Mountains caves is shown on a 1:500 000 scale map, indicating the cavity’s geographic position.