- Category: Geographic Feature
- Type: Valley
- Latitude/Longitude: 52°52'57"N 3°29'4"W
- Eastings/Northings: 300204, 332700
- OS Grid: SJ002327
- Mapcode Local: GBR 6K.QD2K
- Mapcode Global: WH677.FTY2
Location and coordinates are for the approximate centre of Cwm Sian Llwyd within this administrative area.
Geographic features and populated places may cross administrative borders.