Millions of years ago, the Börzsöny volcano rose nearly 2,000 metres above sea level. Subsequent eruptions and severe erosion have left the highest point - the 939-metre-high Csóványos - "only" twentieth on the list of the 100 highest Hungarian peaks.
Due to its formation, the Börzsöny is one of the most untouched mountain ranges in Hungary. On the more than 10 km long ridge of the High Börzsöny, 800-metre peaks line the rim of the former caldera (which came into geological use with the Spanish word 'cauldron').
The "peak" of the Börzsöny has never been a place where man has stayed for long periods of time, and the forces of nature are still at work here today, working freely on inappropriate or inappropriately scaled structures. Obviously, the andesite that forms the main mass of the mountain range and the woodlands, which suggest a considerable amount of wood, have always attracted people, but it is no accident that settlements have remained in the peripheral areas and the basins that surround them. The desire to exploit forest and mineral wealth gave birth to the third narrow-gauge forest railway line in our country between Kismaros and Királyrét, the construction of which in 1893 was followed by the construction of hundreds of kilometers of branch lines. The lines, often intended to be temporary, were installed in side valleys and were highly exposed to the vagaries of nature.
The mountain range is extremely rich in surface water (also due to volcanic activity). Its springs number around 400, a tenth of which occur above 600 meters. In the deep valleys, small streams rush towards the Danube or the Ipoly.
The varied surface has a diverse fauna. Of the 1 200 or so plant species living here, national rarities such as the native Hungarian husk or the red-headed reed canary grass, found only in Börzsöny in Hungary, stand out.
Beech is the dominant tree species on the surface above the oaks of the lower regions. The old beech forests, with their many dead trees, are home to important fauna, including insects such as the hermit beetle, which has a peculiar life cycle, and the beech woodpecker, the symbol of the national park. Among the more conspicuous groups, such as birds, protected species such as the little flycatcher and the white-backed woodpecker are of great value, but the forest-associated black stork and the large-bodied great horned owl, which can even scare people away from its nesting site, are also often seen.
The quality of the forest habitat is indicated by the widespread presence of the wildcat and its larger relative, the lynx, which has been present for decades.
The Börzsön Landscape Protection Area was created in 1978 as a pledge for the long-term preservation of natural values, and its extension forms one of the cores (along with the Pilis-Visegrád block) of the Danube-Ipoly National Park, which was established 20 years later.
The Charnai block around the valley of the Black Stream, which drains the waters from the caldera, is a unique opportunity for the free flow of natural processes, being part of the national park's no-managed zone.