Eidyn was the region around modern Edinburgh in Britain's sub-Roman and early medieval periods, approximately the 5th-7th centuries. It centred on the stronghold of Din Eidyn, thought to have been at Castle Rock, now the site of Edinburgh Castle, and apparently included much of the area below the Firth of Forth. It was the most important district of the Brittonic kingdom of Gododdin, and a significant power in the Hen Ogledd, or Old North, the Brittonic-speaking area of what is now southern Scotland and northern England.