The Plains of Denaria are a wasteland characterised by a rocky, dusty and barren landscape. It's unknown which part of the land of Albion the Plains are located, but it's likely that they are somewhere between the city of Camelot or The Valley of the Fallen Kings (since Morgana's Hovel, where she took care of Morgause, is likely to be there) and it is close to the Isle of the Blessed.