The highest mountains in Yorkshire all lie in the Pennines on the western side of the county, with millstone grit and limestone forming the underlying geology and producing distinctive layered hills. The county top is the remote Mickle Fell (height above sea level) in the North Pennines southwest of Teesdale, which is also the highest point in the North Riding. The highest point in the West Riding is Whernside (height ) near to Ingleton in the Yorkshire Dales. Together with nearby Ingleborough (height ) and Pen-y-Ghent (height ), Whernside forms a trio of very prominent and popular summits (the Yorkshire Three Peaks) which can be climbed in a challenging single days walk. The highest point in the Yorkshire part of the Peak District is Black Hill (height ) on the border with historic Cheshire (which also forms the historic county top of that county). The hill ranges along the eastern side of Yorkshire are lower than those of the west. The highest point of the North York Moors is Urra Moor (height ). The highest point of the Yorkshire Wolds, a range of low chalk downlands east of York, is Bishop Wilton Wold (height ), which is also the highest point of the East Riding. The view from Sutton Bank at the southeastern edge of the North York Moors near Thirsk encompasses a vast expanse of the Yorkshire lowlands with the Pennines forming a backdrop. It was called the finest view in England by local author and veterinary surgeon James Herriot in his 1979 guidebook James Herriot's Yorkshire.