Caves of the Medves - Ajnácsk ői Mountains

The Medves - Ajnácsk ői Mountains form part of the Northern Hungarian Mountain Range. The major part, (300km²) lies in Slovakia, only 100 km² of it belongs to Hungary.

The base of the mountains is a denudated Miocene sedimentary formation. The mountains have witnessed a great deal of volcanic activity. This activity began with two andesite laccolith intrusions.

Later, at the boundary of the Pliocene and Pleistocene about 100 explosion craters were formed, from which copious quantities of basalt lava poured. Between the basalt plateaus deep erosion valleys were formed. Ninety-six natural caves are known and 8 artificial cavities, considered as caves, are listed.

Fifty-nine caves are in Slovakiaand 37 in Hungarian territory. The caves mainly are in basalt and in one case in sandstone.. One cave, found in andesite, "Farkas-lyuk"was destroyed by quarrying, one cave in rhyolite tuff and the artificial cavities have been excavated in andesite tuff.

Several syngenetic caves were discovered in the region. "Ebeczkého jaskyňa" (Ebeczky Cave) and Kis-kői Basalt Cave originated from steam explosion."Studna na Ragáči" ("Ragácsi-kürtő") and "Baglyas-kői-bazaltüreg" are fumarola caves.

The postgenetic caves are fissure caves mainly created by tectonic movements."Ládova trhlina" ("Jeges-hasadékbarlang") and " Nyáryhojasky ňa" (Nyáry Cave) were formed at the same time as the outcroping rim of the rock formation. "Dolna jaskyňa v Zabode" (Zabodai-alsó Cave) developed perpendicular to the rim of the outcrop. Some of the tectonic caves, for example "Skautská jaskyňa" (Cserkész Cave) and "Hviezdicová jaskyňa" (Csillag Cave) were formed by rock disintegration along the clusters of fissures and they are similar to pseudocaves. Of course genuine pseudocaves have also developed amongst the huge basalt boulders as for example "Labirintová jaskyňa" (Labirintus-barlang) or "Zapadna sut’ova" ("Nyugati-görgetegbarlang"). Szilvás-kői Cave and "Pók-lyuk" represent an interesting genotype. They are caves which formed as a result of the collapse of the abandoned coal mines beneath the region.

The Medves-Ajnácskői Mountains have 31 caves longer than 10 m, and even 11 of the basalt caves are more than 30 m in length as follows:

Forty-four caves can be found near Stará Basta in the rim of "Pohánsky hrad" ("Pogányvár") Plateau. Thirty-one caves are in "Szilvás-kő" near Rónabánya. The total length of the natural cavesis 1440 m (of  this 1010 m is in Slovakia).