This round barrow perches on the top of Mynydd Dinas. The barrow's name means 'look out mound'. Mynydd Dinas implies a fortification or settlement of some sort, but there doesn't seem to be any trace. You can see an aerial photo of the mountain at http://www.ggat.org.uk/historic%20landscapes/Rhondda/English/Rhondda_028.htm
which is part of the Glamorgan and Gwent Archaeological Trust website.