Rhondda Cynon Taff, or RCT (Welsh: Rhondda Cynon Taf), is a county borough in the preserved county of Mid Glamorgan, Wales. The county borough borders Merthyr Tydfil and Caerphilly to the east, Cardiff and the Vale of Glamorgan to the south, Bridgend and Neath Port Talbot to the west and Powys to the north. Its main towns are Aberdare, Mountain Ash and Pontypridd. Rhondda Cynon Taff is the second most populous local authority area in Wales. See List of places in Rhondda Cynon Taff for a list of towns and villages. The most populous town in Rhondda Cynon Taff is Aberdare with a population of 31,619 (1991 Census).