A southern top of the hill, Mynydd Garn-wen achieves a height of 436m, and carries a trig point further south again at an elevation of 425m.

To the north the broad moorland ridge runs via a poorly defined 425m top and a col at 404m elevation just south of a minor east–west road, into Mynydd y Garn-fawr, east of Blaenavon.

Beneath these are a series of limestones of different character, some of which are dolomitised and some of which have been quarried for lime production and in connection with the former ironworking industry.

The whole sequence dips slightly to the west into the coalfield and is crossed by a number of small geological faults.

Various restricted byways run to its west and north whilst access from the east is gained via public footpaths.