How the Moravian Karst Was Formed: A 380-Million-Year Story

The Moravian Karst sits on limestone between 350 and 380 million years old, formed from the shells of marine organisms settling on the floor of an ancient tropical sea — so the landscape you see today is, quite literally, fossilised seabed pushed up to the surface. Water has been slowly dissolving it ever since, carving out sinkholes, chasms, gorges and more than 1,100 caves. The so-called Vilémovice limestones are the richest in karst features anywhere in the region. A stalactite just one centimetre thick can take decades or even centuries to grow — which is precisely why this landscape is so irreversibly fragile.

QUICK LINKS 🌊 A fossilised sea · 💧 How water carves out caves · 🏞️ A landscape of two worlds · 🕰️ Why it’s all so fragile · ❓ FAQ

Standing on the viewing platform above the Macocha Abyss, you’re looking down into a pit that took literally hundreds of millions of years to form — and one that’s still changing today. The Moravian Karst is one of the few places where you can genuinely see how slowly, and how relentlessly, nature can reshape a landscape.

A fossilised sea beneath your feet

The limestone that the entire Moravian Karst is carved from is no ordinary rock — it’s formed from the shells of marine organisms that settled on the floor of a warm, shallow sea between 350 and 380 million years ago. In geological terms, these are Palaeozoic limestones, more precisely Devonian. In other words, every rock face you see here was once part of a coral reef or the seabed itself.

The richest in karst features are the so-called Vilémovice limestones, named after the village of Vilémovice and forming part of a geological unit known as the Macocha Formation. It’s here that you’ll find the greatest concentration of caves, chasms and other karst formations in the whole region.

The Moravian Karst itself consists of a belt of Devonian limestone 24 kilometres long and 3 to 6 kilometres wide, stretching from the Brno districts of Líšeň and Maloměřice all the way to Sloup and Holštejn in the north. Covering an area of roughly 100 km², it’s the most fully developed karst landscape anywhere in the Czech Republic.

A tip for fossil enthusiasts: in the youngest limestone layers along the southern edge of the karst, around the villages of Mokrá, Březina and Křtiny, fossils of trilobites — marine arthropods that once lived on the floor of the warm Devonian sea over 360 million years ago — are still being found today. Tomáš Viktorýn, an amateur collector from Brno, has described several species previously entirely unknown in the Czech Republic. The Moravian Karst is still yielding palaeontological discoveries, even after more than a century of research.

How water carves out caves

Limestone has one property that makes it the perfect material for karst formation: it dissolves in mildly acidic water. As rainwater passes through the air and soil, it absorbs carbon dioxide and becomes weakly acidic — and over millions of years, water like this can slowly dissolve limestone along cracks and fissures in the rock. The result is:

• Sinkholes — circular depressions on the surface where water disappears underground.
• Sinking streams — places where streams flowing in from the surrounding non-karst landscape (the Drahany Highlands) literally vanish underground, usually after just a few hundred metres on the surface.
• Chasms — like the Macocha Abyss, formed when the ceiling of a vast underground chamber collapsed.
• Caves — the Moravian Karst has over 1,100 recorded caves, though only five are open to the public.
• Springs — places where underground water re-emerges at the surface, often some distance away and looking like an entirely different river.

This is exactly what happens with the River Punkva: it’s born deep underground in the Amateur Cave, where the Sloup Stream meets the Bílá Voda, flows through the underground system, and finally emerges into daylight near Skalní Mlýn — a journey that today’s tourist boat trip through the Punkva Caves (Punkevní jeskyně) retraces.

A landscape of two worlds

Above ground, you’ll find sun-drenched limestone plateaus and deeply cut valleys — known locally as žleby, or gorges — which in the northern part of the region plunge as deep as 150 metres. The combination of the cold, permanently shaded gorge floors and the warm, sun-exposed upper slopes creates a striking temperature and vegetation inversion: cold-loving upland plants grow down at the bottom of the gorges, while heat-loving species are found up on the slopes above — the exact opposite of what you’d normally expect.

Below the surface is an entirely different world — damp, dark, with a temperature that stays constant at around 7 to 9°C regardless of the season. It’s precisely this stability that draws thousands of bats here to hibernate each winter: they wouldn’t survive outside, but a cave with a constant temperature suits them perfectly.

Why it’s all so fragile

The stalactites you’ll admire in the caves grow incredibly slowly — a single centimetre of stalactite material typically takes decades, sometimes centuries, to form. That means if a careless visitor snaps off a piece of one, the damage won’t be repaired within their lifetime, and quite possibly not within their grandchildren’s either. Comparing century-old photographs of the Punkva Caves with their present-day condition shows just how much decoration has already been lost — whether through the actions of undisciplined visitors, or through processes where human influence can neither be proven nor ruled out.

This is exactly why strict rules apply throughout the whole protected landscape area — you can read more in our article on the rules of the Protected Landscape Area.

Frequently asked questions

How old is the limestone that makes up the Moravian Karst? Between 350 and 380 million years old, dating from the Palaeozoic (Devonian) period.

Why does limestone dissolve in the first place? Rainwater absorbs carbon dioxide from the air and soil, becoming weakly acidic — and water like this can slowly dissolve limestone along cracks over millions of years.

How many caves are there in the Moravian Karst altogether? Over 1,100 have been recorded, though only five are open to the public.

How fast do stalactites grow? Roughly a centimetre every few decades to a few centuries — which is why any damage is practically irreversible within a human lifetime.

What are the Vilémovice limestones? A specific type of limestone named after the village of Vilémovice, the richest in karst features anywhere in the region.

Part of the series A Week in the Moravian Karst: A Complete 7-Day Itinerary. Follows on from the rules of the Protected Landscape Area and Hidden Stories of the Moravian Karst. Sources: Skořepa, H., Tůma, A. — “CHKO Moravský kras šedesátiletá”, Živa 6/2016 (Academia Publishing House, Czech Academy of Sciences); Balák, I. — “Moravský kras: jeskyně a člověk”, Cave Administration of the Czech Republic, 2019; official leaflet of the Nature Conservation Agency of the Czech Republic, “Moravský kras — Chráněná krajinná oblast” (2019); Nedocenění moravští trilobiti, Přírodovědci.cz.