My current favourite walk is along the Oxford canal. Obviously it’s flat (apart from a few locks) but the views are stunning, bird life is lovely and I get to meet all sorts of great people going about their business on the water.
I will be cycling along the towpath from Thrupp to Oxford in a few weeks time. A friend of mine has a boat at Thrupp so I will be riding over from my sister's house in Leighton Buzzard to see the boat and have a chat with him. I am travelling back from Oxford by train.
The Rochdale canal passes down the Calder Valley and the towpath is a nice walk (or cycle ride - as long as you choose a time when there are not too many walkers on it).
EDIT: I don't know how I posted the first picture twice - I deleted the duplicate!