The Pennines /ˈpɛnaɪnz/ are a range of mountains and hills separating North West England from Yorkshire and North East England.Often described as the ""backbone of England"", the Pennine hills form a more-or-less continuous range stretching northwards from the Peak District in Derbyshire, around the northern and eastern edges of Lancashire and Greater Manchester, through the Yorkshire Dales past the Cumbrian Fells to the Cheviot Hills on the Anglo-Scottish border. North of the Aire Gap, the Pennines' western spur into North Lancashire forms the Bowland Fells, and south of the gap is a spur into east Lancashire, comprising the Rossendale Fells and West Pennine Moors. The Pennines are an important water catchment area with numerous reservoirs in the head streams of the river valleys.The region is widely considered to be one of the most scenic areas of the United Kingdom. The North Pennines and Nidderdale are designated Areas of Outstanding Natural Beauty (AONB), as are Bowland and Pendle Hill. Parts of the Pennines are incorporated into the Peak District National Park, the Yorkshire Dales National Park and the Northumberland National Park. Britain's oldest long-distance footpath, the Pennine Way, runs along most of the Pennine chain and is 268 miles (429 km) long.The Cheviot Hills, separated by the Tyne Gap and the Whin Sill, along which run the A69 and Hadrian's Wall, are not part of the Pennines but, perhaps because the Pennine Way crosses them, they are often treated as such. Conversely the southern end of the Pennines is commonly said to be in the High Peak of Derbyshire at Edale, the start of the Pennine Way, although hills continue towards the Stoke-on-Trent area in Staffordshire and into southern parts of Cheshire and Derbyshire.