My local favourite is up Whitbarrow Scar, a great slab of limestone in South Lakeland which is just 10 mins drive away. You run up into the forest, up a very steep hill which gets you to the top in about 17 mins, then you can run along the flattish ridge of the scar and pick a number of ways down and back skirting around the base of the hill on forest tracks through the woods; the quickest is 1 hr but can be extended for another 30-60 mins.
It has a really wild feeling, there's hardly ever anybody there and the atmosphere varies incredibly depending on season, weather, time of day etc. I love running there on my own first thing or at dusk.
From the top you can see the whole Morecambe Bay estuary, and 180 degrees of South Lakes fells; looking east you can see Ingleborough and the Howgills. Fantastic, may go there tomorrow am having written this.