The North Wessex Downs Area of Outstanding Natural Beauty (AONB) is located in the English counties of Berkshire, Hampshire, Oxfordshire and Wiltshire. The name North Wessex Downs is not a traditional one, the area covered being better known by various overlapping local names, including the Berkshire Downs, the North Hampshire Downs, the White Horse Hills, the Lambourn Downs, the Marlborough Downs, the Vale of Pewsey and Savernake Forest. Topography The AONB covers an area of some . It takes the form of a horseshoe, with the open end facing east, surrounding the town of Newbury and the River Kennet catchment area. The northern arm reaches as far east as the suburbs of Reading in mid-Berkshire and as far north as Didcot in South Oxfordshire, whilst the southern arm extends to Basingstoke in northern Hampshire. To the west, the AONB reaches as far as Calne and Devizes. The highest points are the 297 m (974 ft) summit of Walbury Hill, situated southeast of Hungerford in West Berkshire (and the highest point in southern England east of the Mendip Hills), and the Milk Hill-Tan Hill plateau northeast of Devizes in central Wiltshire, at 295 m (968 ft) above sea level. At its northeast extreme, Lardon Chase within the North Wessex Downs AONB faces across the Goring Gap to the Chilterns AONB on the other side of the River Thames. From here working anti-clockwise around the horseshoe, the Berkshire Downs have a steep scarp slope facing north over the Vale of White Horse and a gentler dip slope facing south into the valley of the Kennet. This area includes the horse-racing village of Lambourn and is hence sometimes known as the Lambourn Downs. Beyond the town of Marlborough the downs (now called the Marlborough Downs) sweep in a semicircle to the south around the headwaters of the River Kennet, with the Vale of Pewsey cutting through these downs carrying the headwaters of the Hampshire River Avon. Here too can be found the wooded area of Savernake Forest. Finally, the highest stretch of the Downs runs east along the Berkshire-Hampshire border on the opposite side of the River Kennet from the Berkshire Downs. Again the scarp slope is to the north (facing down in the valley of the Kennet) and the dip slope is to the south into Hampshire. Geology and natural history The downland is part of the Southern England Chalk Formation which