 Many of the high hills are occupied by moors with peat-mosses, the higher ground being uncultivable and barely fit for pastures.As with much of the landscape of the Pennines, they are generally upland areas of high moorland indented by the more fertile valleys of various rivers and streams.The Durham Dales constitute the principal watershed for the county of Durham, as well as contributing to those of the neighbouring counties of Cumbria, Northumberland and North Yorkshire.