 The Rhondda Valley is located in the upland , or Blaenau , area of Glamorgan . The landscape of the Rhondda was formed by glacial action during the last ice age , as slow moving glaciers gouged out the deep valleys that exist today . With the retreat of the ice sheet , around 8000 BC , the valleys were further modified by stream and river action . This left the two river valleys of the Rhondda with narrow , steep sided slopes which would dictate the layout of settlements from early to modern times . 
