Original: At its historic extent, Durham included a main body covering the Catchment of the Pennines in the west, the River Tees in the south, the North Sea in the east and the Rivers Tyne and Derwent in the north.
Simplified: Historic County The historic county covered from the Pennines in the west, the River Tees in the south, the North Sea in the east and the Rivers Tyne and Derwent in the north.