The Alyn Valley

Altitude 450m

Personal experience? : about 30 times

Local area

The Alyn is a small river that rises up in the Clwydian mountain range, and meanders down through the hills to finally drain into the river Dee near Mold. The Clwydian mountains are made chiefly of limestone, which happens to be water soluble. As the river passes through the Pant-y-Mwyn area, a steep sided gorge has formed, which contains most of the caves worthy of mention in the area.

Until the turn of the century, the river was still highly active, and most of the cave systems underwater and hence undiscovered. However, mining activity in the area, or more specifically the Milwr tunnel being driven inland from the sea, lowered the water table drastically, and the river more or less dried up. As a result, the cave systems slowly emptied, and laid in wait to be discovered.


During the early seventies, the North Wales Caving Club were highly active in the area looking for caves. This was a good bet as the river when flowing often disappeared into sinkholes and reappeared elsewhere, often in volume, so the chance of finding decent sized cave systems seemed good. Small amounts of digging took place, and Ogof Hesp Alyn was discovered right on the river bank. The entrance drops immediately vertically down 20 feet from river bank level, and hence is far below the river, thus making caving during flood conditions rather stupid if not fatal in this particular cave.

Further investigation showed the presence of another cave, but digging had to stop for winter. When NWCC reappeared in the spring to recommence digging, they found someone else had finished the job for them!. The cave was consequently named 'Poachers'.

The present

Both Hesp Alyn and Poachers are worthwhile cave systems to explore, Poachers is a nice introduction to caving, and Hesp Alyn is easy to start with, but becomes much more 'sporting' as you get further into it. The valley offers a number of other smaller caves, notably Ogof Nadolig, which is a nice short through trip. Further up the valley, near the Loggerheads country park, a series of small caves can be found, namely Leet caves, nos. 1 to 8. Most of them are insignificant little holes, but recent work has obviously borne fruit as a locked manhole lid has appeared on the river bank!. You can peer through to get a tantalising glimpse of a small passage with running water disappearing into the darkness.

What about it?

The Alyn valley is the nearest caving as opposed to mining to Bangor University and hence we used the caves extensively for training and introducing novices to the sport.

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Last modified on: 25th August 2017 by email the webmaster

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