A former manorial wood, still subject to common rights, covers an area of 50 ha. (124 acres); contains coppice oak.
Allt-y-rhiw is located in the upper Ogwr Valley to the immediate SW of Blackmill. It lies on the NW-facing side of the valley and covers an area measuring some 2km long (NE-SW) by 0.4km at its widest, an area of 50 ha. (124 acres).
It is a rare example of a wood still subject to common right of access. Mentioned in a manorial survey of 1632 it is almost purely sessile oakwood with a few scattered specimens of other trees such as hazel and birch. The ground flora is restricted and the abundance of seedling trees indicates that the wood is self-regenerative. The trees are of varying ages with a wide range of diameters but only 5m-10m high, depending on aspect and exposure. The older stems are gnarled and bushy, probably the result of frequent coppicing and/or lopping - the normal methods of medieval woodland management.
At the time of visiting no earthworks were noted within or around the wood leaving it exposed to grazing sheep which enter it from open land to the E.
visited: D.K.Leighton 22 January 1991