- Category: Water Feature
- Type: Island
- Latitude/Longitude: 53°25'11"N 4°20'28"W
- Eastings/Northings: 244507, 393996
- OS Grid: SH445939
- Mapcode Local: GBR HMNN.N4M
- Mapcode Global: WH421.89YN
Location and coordinates are for the approximate centre of Garreg Costog within this administrative area.
Geographic features and populated places may cross administrative borders.