A rail-trail circuit through Durham, Consett and Newcastle. Most paths are unpaved but firm.
It's a steady climb up to Consett, but never too steep. The paths along the Tyne are justly celebrated and offer superb views of the Newcastle/Gateshead bridges.
Combine it with NCN 1 along the coast past Sunderland for a full circular tour. For most of the route, you'll hardly see a car.