To be honest I'm not sure this should actually count as 'fieldnotes' since the long, south-eastern ridge of Mynydd Troed is thickly covered with heather this overcast September afternoon, rendering positive identification of anything but a massive cairn difficult, to say the least. So that's us buggered, then.
But these things happen and, for me, it is the dominating presence of the Pen Allt-mawr ridge (to the south-east) which is the most noteworthy aspect of this spot. Hey, perhaps that's the reason the funerary cairn was placed here, a considerable distance away from the summit of Mynydd Troed... to face other, perhaps more 'senior' people interred upon the higher ridge across the way? [Pen Allt-mawr is obscured by the ridge from the summit, by the way].
The walk down the ridge affords the opportunity to view a number of other monuments from new angles... the Caeau enclosure across beautiful Cwm Sorgwm, its obscure earthworks nicely defined... Castell Dinas and the Bwlch Bach a'r Grib cairn.... the long cairn at the bwlch with Mynydd Llangorse... to name just a few. In short, it's difficult to know which way to look, such is the quality of the landscape. We solve the conundrum by weaving in a 'serpentine' manner across the ridge as we return to the summit. To our right (east) the skyline is totally dominated by the great mass of The Black Mountains (of which Mynydd Troed) is an outlier, whilst either side of Talgarth , to the north, long cairns proclaim the relative fertility of the red soil here [Penyrwrlodd and Ffostyll]. And, of course, a further long cairn lies below us to the approx south-west, the promontory fort upon Mynydd Llangorse rising above, the funerary cairn upon Pen-y-Fan in turn dominating all, looming beyond the crannog-endowed Llyn Syfaddan (Llangorse Lake). Sheer sensory overload.
The climb from the parking area near the long cairn is steep - very steep in places - but relatively short and, as Elderford mentions, an easier alternative path diverting to the right is available some way up. Worth the effort, you could say.
Another example of an upland funerary cairn sited at a point other than the summit area of a mountain... in this case significantly so, near the southern extremity of Mynydd Troed's long ridge. According to Coflein:-
'Remains of a burial cairn situated in open moorland on the S end of the Mynydd Troed ridge. Stone built and roughly circular on plan, measuring about 9.5m in diameter and up to 0.6m in height. Source: Cadw scheduling description. F. Foster 17/03/2005'