Uamh an Claonaite

Uamh an Claonaite is the longest cave system in Scotland, set in the limestone hills of Assynt in Sutherland, in the north-west Highlands. Its entrances lie close to the Bone Caves near the hamlet of Inchnadamph. It is a site for experienced cavers and cave divers, and for most visitors it is a reason to explore the surrounding geology rather than a place to enter.

What is Uamh an Claonaite?

The Gaelic name simply means a cave, and the whole area carries Gaelic place-names. The system combines dry passages with at least six sumps, the flooded sections that can only be passed by diving. Published lengths differ. Wikipedia lists 2,868 m with a vertical range of 110 m, while the Grampian Speleological Group's cave registry gives about 3,426 m. A fair summary is roughly 3 km, and by any measure it is the longest cave in the country.

What makes it special?

The cave formed in Durness limestone. Flowstone from abandoned, dry passages has been dated radiometrically at between about 12,000 and 192,000 years old, a useful record of past climates in northern Scotland.

Water from several caves in the Allt nan Uamh valley drains to one shared resurgence, Fuaran Allt nan Uamh. The mapped passages cover only a small share of the roughly 2 km between the sinks and the outlet, so much of the system may still be unexplored.

How was it explored?

Exploration took decades. Cavers reached sump 6 in 1990, and in 1995 Simon Brooks and Mike O'Driscoll dived sump 6b, opening up far more of the cave. The breakthrough came in December 2007, when digging at the nearby Rana Hole reached the final chambers and bypassed the sumps. One of the remote chambers is known as the Great Northern Time Machine.

Can you go inside?

Water is the main hazard. After heavy rain the main passage floods in several places and some sections become impassable. A trip needs experience, proper kit and, in practice, contact with a local caving club. Visitors without that background should stay out.

What else is there to see nearby?

The Inchnadamph valley lies within a nature reserve and the North West Highlands Geopark. The easiest target is the Bone Caves, where bones of Ice Age animals including bears and reindeer have been found. You also get limestone scenery, springs emerging from the hillside and views toward Assynt's mountains such as Ben More Assynt and Conival.

When should you visit?

Late spring and summer are best, with long days and steadier weather. Check the rainfall forecast first, because Sutherland weather turns quickly and cave water levels can rise fast.

Frequently asked questions

Is Uamh an Claonaite open to tourists?

Not as a conventional attraction. There is no visitor infrastructure, and the cave demands caving skills, with diving for its deeper parts. Walkers can visit the nearby Bone Caves instead.

How long is the cave?

Between about 2.9 and 3.4 km depending on the source, because different surveys give different totals.

How many sumps does it have?

At least six, explored over successive years. Since 2007 the far chambers can also be reached through Rana Hole, which avoids some of them.

Where is Uamh an Claonaite?

In Assynt, Sutherland, in north-west Scotland, near the hamlet of Inchnadamph and within the North West Highlands Geopark.