Geograph - photograph every grid square

This relatively remote spot now receives more visitors than once it did as the route of the Beacons Way passes through. Go back a century and more and the slopes would have witnessed the sound of pick and shovel as the numerous small limestone quarries were worked on the flanks of Foel Fraith. The great depression in the saddle between that hill and Garreg Las is one of the largest natural depressions in Wales and formed by the dissolution of the underlying limestone. One of the oddities of this place is that Blaenllynfell is not, as the name would suggest, at the head of the Nant Llynfell but at the head of the Nant y Llyn instead. Could this be an early OS error?