Last updated: April 14, 2026
Beneath the surface of the Moravian Karst lies a hydrological network that has taken millions of years to develop. Water enters the limestone through fractures, sinkholes and stream sinks, dissolves the rock as it descends and eventually concentrates into underground rivers that flow through cave systems before re-emerging at springs in the valley floors. The largest and most complex of these underground rivers is the Punkva, which passes through the Amaterska Cave — the longest mapped cave system in Czech Republic at approximately 35 kilometres of documented passages. Along the same limestone terrain, caves such as Byci Skala and Bicovska have produced significant paleontological and archaeological deposits, providing evidence of both Ice Age megafauna and Bronze Age human activity in underground environments.
The Amaterska Cave System
The Amaterska Cave (Amaterska jeskyne) is the longest cave in Czech Republic and one of the longest in Central Europe. Its currently documented length stands at approximately 35 kilometres of mapped passage, though speleological research continues to extend this figure as new connections are surveyed. The cave occupies the Pustý žleb gorge section of the Moravian Karst, descending through multiple levels before connecting to the Punkva River system at depth.
Discovery of the cave's full extent was gradual. The initial known sections were explored in the early 20th century, but the connections between separate cave segments — particularly the section linking the Amaterska passages to the upper Punkva drainage — were confirmed only in 1975 after a major diving survey. The cave contains several sumped passages (sections entirely filled with water) that required scuba diving equipment to traverse. The longest sump in the system extends for approximately 630 metres and was first crossed in 1968 by Czech cave divers working without the benefit of modern diving technology.
"At approximately 35 kilometres of mapped passages, the Amaterska Cave is the longest cave system in Czech Republic — and its full extent remains under active survey."
The Amaterska Cave is not open to general visitors. Access is restricted to researchers, speleologists and members of the Czech Speleological Society, who require written permission from the Czech Cave Administration. The restriction is primarily a conservation measure: the cave contains active formations, undisturbed sediment layers and a functioning hydrological system that records changes in groundwater chemistry over time. Scientific studies conducted inside the cave have contributed to research on palaeoclimate, karst hydrology and cave biota — including several invertebrate species found only in the cave environment.
The Punkva River Underground Course
The Punkva River enters the ground near the village of Rudice through a series of swallow holes on the eastern margin of the Moravian Karst. It flows underground for approximately 12 kilometres before re-emerging at Punkevni udoli spring near Skalny Mlyn. Along this course, the river passes through the Amaterska system and then through the publicly accessible Punkva Caves section, where the boat tour operates. The water level in the underground river fluctuates significantly: during normal flow, boats navigate the passage at a ceiling clearance of 1 to 2 metres; after heavy rainfall, the same passages can fill completely, flooding the cave tour route and requiring temporary closure.
The spring at Punkevni udoli discharges an average of roughly 300 litres per second under normal conditions. During major flood events following heavy snowmelt or prolonged rainfall, discharge has been recorded at over 30,000 litres per second — a factor of 100 increase — demonstrating the high hydraulic sensitivity of a karst drainage basin compared to surface catchments with soil buffering.
Byci Skala Cave — Bronze Age Deposits and Ice Age Remains
Byci Skala (Bull Rock Cave) is one of the most archaeologically significant cave sites in Czech Republic. Located in the Prosti žleb gorge of the southern Moravian Karst, it was excavated in the late 19th century by the Czech archaeologist Jindrich Wankel (1821–1897). The deposits yielded a Bronze Age assemblage dated to the Hallstatt period (approximately 800–600 BCE), including bronze jewellery, iron tools, horse bones, human skeletal remains and evidence of metal-working. The presence of numerous complete bronze items and human bones led to interpretation of the site as a ritual deposit or a location of violent conflict; the question has not been definitively resolved in the literature.
Underneath the Hallstatt layer, Wankel's team recovered Pleistocene animal bones including cave bear (Ursus spelaeus), wolf, wolverine, cave lion and woolly mammoth. These remains date to the last glacial maximum, roughly 20,000 to 25,000 years ago, when the cave served as a natural trap and denning site for large carnivores. The original Byci Skala assemblage is held at the Moravian Museum in Brno; a selection is on permanent display in the prehistoric section of the museum.
Bicovska Cave
Bicovska Cave (Bicovska jeskyne) is a smaller cave system in the southern section of the Moravian Karst, notable for its relatively intact sediment profile and preserved speleothem (stalactite and stalagmite) sequence. Unlike the major publicly accessible caves of the northern Moravian Karst, Bicovska is not on the general visitor circuit and is managed primarily as a scientific reference site. Sediment samples from its floor have been used in palaeoclimate studies to reconstruct precipitation patterns in Moravia during the Holocene (the last 11,700 years). The cave contains a section of actively forming flowstone that has been subject to uranium-thorium (U-Th) dating, establishing a deposition chronology that correlates with climate records from ice cores and lake sediments elsewhere in Central Europe.
Speleothem Records as Palaeoclimate Archives
One of the principal scientific uses of the Moravian Karst cave systems is the extraction of palaeoclimate data from cave formations. Stalagmites grow in annual to sub-annual increments under conditions where the growth rate, isotopic composition and trace element chemistry reflect the temperature and precipitation regime at the surface above. Sampling a cross-section of a stalagmite and measuring oxygen isotope ratios (δ¹⁸O) and the ratio of magnesium to calcium along the growth axis produces a proxy climate record extending as far back as the formation's base. Stalagmites from Moravian Karst caves have yielded continuous records extending to 120,000 years before present, covering the transition from the penultimate glaciation through the last interglacial and into the most recent glacial cycle.
Research groups from Charles University in Prague, Masaryk University in Brno and the Czech Academy of Sciences maintain active sampling programmes in the Moravian Karst caves, working under permits from the Czech Cave Administration. Published results appear regularly in journals including Quaternary Science Reviews, Earth and Planetary Science Letters and Journal of Cave and Karst Studies.
Cave Fauna and Endemic Species
The deep cave environments of the Moravian Karst support a specialised fauna adapted to darkness, stable low temperatures (7–9°C year-round) and limited food input. Documented taxa include cave-adapted beetles of the genus Leptodirus and Anophthalmus, isopod crustaceans in the underground water, several bat species using the caves for hibernation (greater horseshoe bat Rhinolophus ferrumequinum, lesser horseshoe bat Rhinolophus hipposideros and brown long-eared bat Plecotus auritus), and micro-organisms in the cave water and sediment that have been subject to microbiological survey since the 1990s. Bat counts conducted by the Czech Bat Conservation Trust record between 4,000 and 6,000 overwintering bats in the accessible sections of the Moravian Karst cave network in recent winters.
