Three enclosures, noted through aerial survey (14.10.2009), are located on moorland on the south side of Mynydd-y-glog, to the immediate north of the Heads-of-the-valleys A465 road.
The features are oval or sub-oval enclosures defined by shallow `ditches? or cuts made in the turf.
1. SN98960819: northernmost, oval 92m (NW-SE) by 51m defined by a 2m-3m wide cut 0.25m deep with an uneven stony base.
2. SN98940805: central and largest of the three, sub-triangular in shape, 103m (NW-SE) by 63m wide at its south-east end. This one is defined by a narrower cut, 1m-2m wide and 0.25m deep with a stony base. At its north-west end projects an arcuate bank 23m long curving to the north. This enclosure is transected by a post-and-wire fence.
3. SN98990798: southernmost, sub-oval 59m (NE-SW) by 40m, defined by a shallow ditch 1m-1.5m wide and 0.2m deep indistinct on its south-east side where it has become overgrown with boggy vegetation. Located entirely on the south side of the fence.

These features do not look particularly ancient yet no obvious function can be ascribed to them.

David Leighton, RCAHMW, 8 November 2011