- Category: Water Feature
- Type: Island
- Latitude/Longitude: 53°23'12"N 4°15'1"W
- Eastings/Northings: 250427, 390134
- OS Grid: SH504901
- Mapcode Local: GBR HMWR.7QN
- Mapcode Global: WH428.P44F
Location and coordinates are for the approximate centre of Garreg Allan within this administrative area.
Geographic features and populated places may cross administrative borders.