Mynydd Llangynidr

A further tributary, the Nant Milgatw, reaches in from the south whilst the sharp edge of Rassau Industrial Estate also defines a part of its southern margin.

[1] Mynydd Llangynidr is formed from a layer cake of Palaeozoic Era sandstones and limestones which dip gently southwards into the South Wales Coalfield basin.

The larger part of the mountain has a pock-marked appearance due to the hundreds of shakeholes in its surface arising from the presence of the limestone beneath the sandstone cover.

The less frequently exposed sandstone of the southern part is the lowermost Westphalian age Farewell Rock which forms the base of the Coal Measures.

[4] The area was proposed for designation as a site of special scientific interest by the Countryside Council for Wales in August 2012 in respect of its karstic geomorphology.

[6] There are a handful of small abandoned workings for sandstone in the Farewell Rock outcrop on the hill's eastern margin in the vicinity of the Beaufort Road.

Llangynidr Reservoir is supplemented by feeder channels constructed across the moor from tributary streams of the Ebbw Fach which otherwise empty into the main river below the dam.