Harlech Castle in Harlech, Gwynedd, Wales, is a Grade I listed medieval fortification built onto a rocky knoll close to the Irish Sea. It was built by Edward I during his invasion of Wales between 1282 and 1289 at the relatively modest cost of £8,190. Over the next few centuries, the castle played an important part in several wars, withstanding the siege of Madog ap Llywelyn between 1294 and 1295, but falling to Prince Owain Glyndŵr in 1404.