. Location The kingdom lay mostly in what is now western Herefordshire in England, its heartland between the River Monnow and River Wye. However, it also spread into modern Monmouthshire and east of the Wye, where sits the old Roman town of Ariconium (Welsh: Din Aricon) at Weston under Penyard from which its name may derive; it may have been the first capital. Some maps Map of Later Cymru (Wales) show Ergyng extending across what is now the Forest of Dean to the River Severn. Monarchy After the… (More on Ergyng)