Baradla Domica cave system

The Baradla–Domica cave system (the Hungarian part is called Baradla cave) is Hungary's oldest explored, best known, stalactite cave visited for centuries. It opens with several entrances on the Aggtelek karst. Its length together with the 5.3‑kilometre Domica cave opening in Slovakia, forming one system, exceeds 25.5 kilometres. Its natural entrance is at the border of the village of Aggtelek, at the foot of the high rock wall that appears white from a distance. The main branch, segmented by ledges and meandering, stretches to the village of Jósvafő and is seven kilometres long. The average rock tunnel is 10 metres wide and 7–8 metres high, widening into a huge chamber in some places. Several shorter and longer side branches join the main branch. A large part of the cave is decorated with stalactites of varied colour and shape, offering an unparalleled spectacle. The Acheron stream, originating from the Acheron sinkhole at the border of Aggtelek village, and the Styx streams coming from the Domica side, now flow through the main branch only during floods. In dry periods the water reaches the Lower Caves at a depth of 30–40 metres via the cave’s water sinks. The cave’s natural entrance has been open since ancient times, providing shelter even for people of the New Stone Age.

Its first written mention dates from 1549. The first survey was carried out in 1794 by József Sartory. Until 1825 only 1.8 kilometres of it were known. This section is depicted on the cave map made in 1802 by the surveyor of Gömör County, Keresztély Raisz, which was the first cave map also published in print. Engineer Imre Vass in 1825 penetrated the Vaskapu spring, which was then the endpoint, and discovered the cave’s main branch of about five kilometres length. He produced an accurate map and description of the cave and the surface. His work was published in Hungarian and German in 1831.

To facilitate cave visits, the first development was carried out in 1806. In 1890 a artificial exit was established at the Red Tone. In 1922, continuing the Stage, which at that time marked the end of the cave, a new 500‑metre long section was discovered, which in 1927–1928 was excavated from the Jósvafő side. In 1932 Kessler Hubert succeeded in proving the connection between the Domica cave and the Baradla cave by penetrating the Styx stream siphons.

Together with the other caves of the Aggtelek Karst and the Slovak Karst, the cave was declared a World Heritage site by UNESCO in 1995. The entire cave system and its catchment area were placed under the Ramsar Convention, which protects wetlands of international importance, in 2001. The most attractive attraction of Aggtelek National Park welcomes visitors all year round, without holidays, offering several hiking routes to choose from.

Environment

In the northeastern protrusion of Hungary, along the Slovak border region, one of the country's most varied karst landscapes is located. The Aggtelek Karst (Aggtelek Mountains, Lower Mountains), belonging to the North Hungarian Central Mountains, forms a unified geological, surface and hydrological system with the Slovak Karst on the other side of the state border. Before the current borders were drawn, the two areas were referred to in the literature as the Gömör–Tornai Karst. On the Triassic basal rock, which is suitable for karstification, a characteristic moderate‑climate mid‑mountain karst surface developed as a result of about five million years of evolution, i.e., since the end of the Carboniferous. Its most striking features are: extensive plateaus with an average height of almost 600 metres; bowl‑shaped depressions characteristic of the destruction of open karst fields, the sinkholes; karst valleys and uvalas with sinkhole chains, and cliffs, karst fields formed on steep, barren mountain slopes. In some places, the water surfaces of small doline lakes sparkle in the blocked sinkholes and water basins, blind valleys line the border between karst and non‑karst fields, where intermittent streams disappear in water basins locally called “fox holes” or “devil holes”. The spectacular surface forms of the region are complemented by smaller and larger caves and cave systems deep underground. Among them the largest is Baradla, whose length together with the Domica opening in Slovakia exceeds 25.5 kilometres. The two caves forming the unified whole exemplify multi‑level cave development and are undeniable evidence of the hydrological connection between the Aggtelek Karst and the Slovak Karst.

Formation

Baradla formed in the region about 230 million years ago in gradually deepening sea deposits of limestone, in the so‑called Middle Triassic limestone. After the Triassic period the area was uplifted, and during mountain building the solid rock blocks were heavily fractured, allowing the cave‑forming power of waters descending from the surface to the depths. In the development of the passages, besides the dissolving effect of the waters that penetrated deep through the water mouths, the abrasive work of the gravelly sediment they carried also played a role. The creation of larger chambers and collapses was influenced by rock‑mechanical and tectonic processes.

The character of the limestones was determined by the depth of the water and the distance from the land. The oldest rock, found between the Jósvafő entrance and the Giants’ Hall, is a dark gray‑black, strongly fractured, thick‑bedded Gutenstein limestone; it allowed passage formation, but its impurity did not favor stalagmite formation. The longest part of the main branch of the cave proceeds in light gray, well‑karstified, stalagmite‑forming Steinalm limestone. A further change of rock is detectable only from the section called Vaskapu to the Aggtelek exits. This also light gray, well‑karstified, relatively pure Wetterstein limestone likewise provided the basis for rich stalagmite development. In the latter two rocks, fossils, green algae, shells, and ammonite remains can be observed.