On a trip out to Wales, I turned down a small side road and passed this very long and high wall. I think it borders the estate for Penryhn Castle, it is at least 12 foot high and follows the twists and turns for at least 1/2 mile down the side of the lane, before it veers off to the left. How long in total it is I don't know, but it must have been a major construction job.
