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Visitor’s guide

The limestone outcrop marks the cave’s entrance.

Did you know that 350 million years ago Ireland lay close to the equator? In fact, Ireland was submerged under a tropical sea rich in marine life. This period in history is called the Carboniferous geological period.

As you begin your tour of this unique and ancient environment, you’ll learn how limestone was formed from the remains of prehistoric creatures, marine life and the lime-mud that settled on the ocean floor. Compressed by the water above, limestone beds formed one after another through time.

As the geological forces of our planet forced the rock beds to move and tilt, mountains were formed, creating fractures in the rock and exposing it to rain and soil water which is acidic.

This acidic environment dissolved the parts of the limestone rock made up of the prehistoric skeletons, allowing fissures to appear and water to make its way through the rock. Over time it created the caves and subterranean world that awes us at Crag Cave today.

When you step below ground, you are entering a world that was formed hundreds of millenia before the dinosaurs or humans roamed the earth!

…and don’t forget to look out for fossils in the cave walls!

After some initial exploration of the caves, in 1983, Martyn Farr, a world-renowned Welsh cave diver made his way through a 24 foot flooded U-shaped passage at the end of Crag Cave Lower. Neither he, nor John Cooper, his fellow cave diver on the exploration, knew what lay ahead.

Mud and silt on the edge of the dive pool obscured their vision on this dangerous expedition into an unknown subterranean world. Shining his torch into the darkness, the “caverns measureless to man” revealed themselves.

Thrilled at the discovery of wondrous caverns, passages and cave formations in Crag Cave, Farr named this cavern “Diver’s Delight” and it became part of the Crag Upper Cave.

The cave was developed between 1987 and 1989 by constructing a shaft (the only man made entrance) and putting in pathways, railings and lights. Cave engineers made the cave safe and a special lighting system was installed to enhance the unique and evocative landscape of the caves.

Thankfully, a passageway now exists to ease our way into Crag Cave!

Do you remember those prehistoric creatures and marine life that played such an intrinsic part in the laying down of the limestone? A mineral called calcium carbonate is stored in the skeletons and shells of the sea creatures who lived in the sea water. Limestone is made up of at least 50% of this mineral.

Limestone itself is non-porous. It has a crystalline structure which means it does not absorb water. But the fissures and fractures that were created in the rock beds by the formation of mountains, exposed the limestone and allowed acidic rain and soil water to run between the fissures. This acidic water dissolved the calcium carbonate, creating an environment where caves begin to develop.

Our “Corn on the Cob” stalactite and the “Soft Mud” stalagmite below it are formed by water dripping from the ceiling and depositing small amounts of that mineral calcium carbonate (now known as calcite).

The stalactite has been dated to be approximately 6,000 years old. It is one of the largest stalactites in the system measuring over 2 meters long.

At this stop, you can move from science to wonder…you will see the oldest part of the cave which is over one million years old. It is formed by a series of tunnels eroding over time and eventually interconnecting with each other.

Being avid fans of J.R.R. Tolkien’s “Lord of the Rings”, the first explorers of the cave named this cavern “Minas Tirith” after the great city of Gondor in Middle Earth.

This chamber was formed by three separate passages joining together and reveals the stream that runs through the cave continually eating into the rock and creating new crevices to explore.

This is still an actively-forming cave system. Who knows what mysteries the hidden earth will reveal in tens of thousands of years’ time?

At this stop, we can see a different type of formation. It’s called flowstone and it is formed by water flowing across the cave’s floors and walls.

You’ll be able to compare a “dead” formation (that is no longer forming) and a feature that is still active.

Drapery features are seen hanging off the edge of the flowstone creating a formation with an alien appearance that at the same time has the familiarity of the stalactites. This section of the cave highlights impurities that enter water as it flows through soil and overlying rocks and stains the formations within the cave creating unusual colours among the pure white calcite.

This entertaining part of the cave allows adults and children alike to have a little fun trying to recognise some everyday items you would find in a kitchen within the cave formations! These can range from food items to glassware so make sure you keep an eye out and get creative!


As Diarmuid and Gráinne fled from the great warrior Fionn Mac Comhaill, they hid in forests and caves, journeying throughout the island over years to escape the jealous, ageing Fionn. We’re told that they spent a night hiding in a cave in the Sliabh Luachra area. We believe this to be Crag Cave.

In our personal rendition, Crag Cave itself has honoured their love by forming an evocative stalagmite.

The location of Diarmuid and Gráinne’s cave is steeped in mythology itself but perhaps there’s still a little magic left in Castleisland?


The candlestick-shaped stalagmites precariously perched on a ledge draws a visitor’s attention upwards to the domed ceiling of “The Cathedral”.

The unusual shape of the stalagmite impresses on viewers the rate of growth for stalagmites and the past climate of Ireland, especially the last time Ireland had a warm, dry climate…ending about 5,000 years ago!

Thousands of straw stalactites drop from a roof of pure white calcite. Coming towards the end of the tour, this is possibly the most spectacular and memorable section of Crag Cave.

The Michelin Guide, who rated Crag Cave with two stars, describes the beauty of the Crystal Gallery as “eliciting gasps of wonder”.

Being hollow in the centre, these straws are exceptionally fragile and occasionally snap off the ceiling under their own weight. In places, the remains of these beautiful formations carpet the cave floor. All the stalactites in the cave, even the large one near the entrance, were once delicate straws that became stronger to create the larger formations that are now seen.

One of Crag Cave’s most famous stalagmites in the cave system, it is said to resemble the Madonna and Child. With a little bit of faith, it is possible to discern Mary holding the baby Jesus in her arms.


Madonna Madonna

Crystal Gallery Crystal Gallery

Diarmuid & Grainne Diarmuid & Grainne

The Kitchen The Kitchen

Divers Delight Divers Delight

Cave Entrance Cave Entrance

Big Stalactite Big Stalactite

Flowstone Flowstone

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