This alignment of Standing stones (literally in Welsh "The Field of the Dead", is located to the west of the Preseli Hills. Listed by Alexander Thom in his "Megalithic Lunar Observatories" he claims it has a sight line with a mountain on the other side of the Irish sea.

Parc y Meirw looking along the stone row

In this picture you can see three of the five stones in the row, which are all now clustered around a gate into a field. The incorporation of the stones into the hedgerow must have happened many centuries ago and gives an eerie sense of the continuity of life far further back than you normally think about.