Wales
Blaen Onneu
541M
1775FT
About Blaen Onneu
Situated on the rugged limestone fringe of the Black Mountains, this high plateau offers a starker character than the nearby sandstone peaks. The terrain is defined by dramatic shakeholes and old quarry workings, providing a weathered, industrial edge to the wide views over the Usk Valley towards Pen y Fan.
Key Statistics
Rank
74th Highest in Wales
Parent Range
Brecon Beacons
Prominence
?
25m
Nearest Town
Llangynidr
Geology
You are walking on layers of limestone and sandstone mixed with smooth pebbles and fine mud. These solid rocks form the sturdy foundation of this rugged landscape.
Classifications
Find It
OS Grid Reference
SO147159
Latitude
51.8352°N
Longitude
3.2394°W
Did You Know?
- •The name is Welsh in origin, where 'Blaen' signifies the 'source' or 'head' of a valley or river—in this case, the River Onneu which drains the southern slopes.
- •The hill is marked by the scars of the Blaen Onneu limestone quarry, which historically supplied the voracious ironworks of the Ebbw Vale and the surrounding industrial valleys during the 19th century.
- •Deep beneath the surface of this plateau lies part of the Ogof Draenen system; discovered in 1994, it has since been explored to a length of over 70 kilometres, making it one of the longest cave networks in the UK.
- •The summit area provides a clear perspective of the 'Three Peaks' of Monmouthshire: the sharp cone of the Sugar Loaf, the hulking Skirrid, and the broad, flat profile of the Blorenge above Abergavenny.
- •Navigating the plateau in mist requires focus, as the landscape is peppered with enough limestone shakeholes to make a direct line feel like a game of subterranean snakes and ladders.