the howardian hills form 79 square miles of well-wooded undulating countryside between the flat agricultural vales of pickering and york. the irregular high ridges of the howardian hills are a southern extension of the rocks of the hambleton hills in the north york moors. jurassic limestone and a network of pasture, extensive woodland, trees and woodland combine to create a strong visual character in the higher ground overlooking the agricultural plains below. on the eastern edge, the river derwent cuts through the hills in the kirkham gorge, a deep winding valley formed as an overflow channel from glacial lake pickering.