Marble Arch Caves
Boats glide through an underground river in Fermanagh, and the 'marble' they pass is really limestone, carved by peat-brown water pouring off Cuilcagh Mountain.
Published
Quick Facts
- Location
- Near Florencecourt, County Fermanagh, on the slopes of Cuilcagh Mountain
- Rock
- Carboniferous limestone, not marble
- First scientifically explored
- 1895, by French caver Édouard-Alfred Martel
- Opened to visitors
- Show cave opened in the 1980s
- Rivers
- The Owenbrean, Aghinrawn and Sruh Croppa rivers feed the cave system and join underground to form the Cladagh River, which flows out of the caves
- Highest point above
- Cuilcagh Mountain, about 665 metres
- Designation
- Core of the Cuilcagh Lakelands UNESCO Global Geopark, which spans the Fermanagh–Cavan border and was formerly called the Marble Arch Caves Global Geopark (renamed in 2021)
- Famous feature
- A boat trip along an underground river
The 'marble' that isn't marble
Start with the name, because it's a good bit of mischief. There is no marble here. The caves are cut into limestone, the grey sedimentary rock laid down in warm tropical seas more than 300 million years ago. The name comes from the Marble Arch itself, a natural limestone bridge in the wooded Cladagh Glen. It is a handsome arch, and early visitors evidently thought it deserved a grander stone than it was made from. The label stuck, and the caves took it on.
A French explorer and a candlelit river
The caves came to wider attention in 1895, when the French cave explorer Édouard-Alfred Martel arrived. Often called the father of modern speleology, Martel had already made his name in the caves and gorges of France. He worked here with the Irish naturalist Lyster Jameson, pushing into passages that had been known only as dark openings where rivers vanished. The pair explored by lamp and candle along the underground water. Their trips put the Fermanagh caves on the map for cavers and scientists, and the arch and glen became a destination for Victorian sightseers.
Why the river is the colour of tea
The water that carved these caverns starts high on Cuilcagh Mountain, a huge peat-covered plateau. Streams run off the blanket bog stained brown, then meet the limestone edge and drop underground. That peaty water is slightly acidic, and over thousands of years it has dissolved passages, chambers and channels in the rock. As it drips through the roof, it also deposits stalactites, stalagmites and delicate curtains of calcite. An underground river is the real star of the show here. Visitors travel part of the route by boat, drifting past formations lit from below, with the water shifting from glassy to loud depending on recent rain.
A cave with a weather forecast
This is a cave that answers to the sky. Heavy rain on Cuilcagh sends water surging through the system, and the show cave can close when levels rise. Even on an ordinary day, the water below your boat comes straight off the mountain. The tour also includes walkways and passages with names that tell their own stories, such as Moses Walk, a sunken walkway below the underground river's water level, with walls holding the water back on either side. Look up as well as down: the roofs are hung with formations that grow only a tiny fraction of a millimetre a year, so each one has been forming for a very long time.
A geopark across a border
The caves are the heart of the Cuilcagh Lakelands UNESCO Global Geopark, which crosses the border between Fermanagh and neighbouring County Cavan. It was formerly called the Marble Arch Caves Global Geopark and was renamed in 2021. It was one of the first cross-border geoparks in the world, which suits a landscape where water pays no attention to lines on maps. Above ground, the geopark takes in blanket bog, upland limestone pavement, sinkholes and wooded glens. Cuilcagh is the high ground that shapes everything below it, and the boardwalk path up its slopes, nicknamed the Stairway to Heaven, has become one of Northern Ireland's most photographed walks.
What to look out for
Before you go underground, spend time in Cladagh Glen. Walk to the Marble Arch and watch the river appear and vanish through the rock. It is the clearest demonstration of how this whole system works. Inside, watch for the colour of the water, the reflections on its surface and the way formations seem to grow out of the dark. Wrap up warmly, because the caves stay cool whatever the weather outside.
Notable people
- Édouard-Alfred Martel
- Lyster Jameson