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 .