Cefn Eglwysilan is a 382m hill high above Pontypridd with twin summits, one of which is crowned by a wireless transmission tower, the other a trig point. You can walk it from many directions, varying in difficulty depending on how low you start. I parked on a fairly nearby layby, giving me a 5.1m loop, with only 748ft of ascent in total.
I skirted the Northern summit, which has the wireless station on it, and as you round the corner and start to head South you get views over Pontypridd below.
I walked it in the evening and only saw one other person on the whole loop, and they were a cyclist.
The views from the trig point are really impressive and well worth the walk, the footpaths are broad and easy to follow and there is a good pub nearby – the Rose and Crown – that you could add to your walk.