Yr Eifl is a range of three hills that dominate the skyline above Trefor. Tre'r Ceiri, the second highest of the hills, has on one of the best examples of a Stone Age or Neolithic settlement in Europe on its summit. Views from the summits, on a clear day, extend to Ireland, the whole of Cardigan Bay, Anglesey, Snowdonia, and the northern mountains of England. The central peak, the tallest at , is called Garn Ganol; the most seaward, and smallest peak, is Garn For, home to the quarry.