I've included this link as proof that the site does exist and is not just a bump in a field.My thanks to the Boss at Mason's yard below,for directions and location and as to what I could expect to find.As described above,it is a Norman ringwork and not a motte.A ringwork is rather like a large quoit,with a defensive ditch on the outer side,a large earthen mound almost all around the site,leaving a narrow opening for a probably,wooden gate.On this site,the entrance/gateway faces north.The image above shows the defensive mound with the now filled-in ditch on the rhs of the mound.The gateway is just to the lhs of the image.see http://www.castlefacts.info/castledetails/castleDetails3.aspx?uin=20724
see http://www.pembrokeshirevirtualmuseum.co.uk/main_menu/places_to_visit/castles/earthwork_castles/castell_cynon/castle_cynon.html
see http://www.coflein.gov.uk/en/site/304253/images/CASTELL%3BCASTELL+CYNON%2C+LAMPETER+VELFREY/
see http://travelingluck.com/Europe/United+Kingdom/United+Kingdom+(general)/_6285854_Castell+Cynon.html#local_map