Chiltern Hills

The Chiltern Hills or the Chilterns ( ) are a chalk escarpment in southern England to the north-west of London, covering 660 mi2 (1,700 km2) across Oxfordshire, Buckinghamshire, Hertfordshire and Bedfordshire. The hills stretch 45 miles (72 km) from Goring-on-Thames in the south-west to Hitchin in the north-east, and are 12 miles (19 km) at their widest. In 1964, 322 mi2 (830 km2) - almost half of the Chiltern Hills - were designated by the Countryside Commission as an Area of Outstanding Natural Beauty (AONB) under the powers established by the National Parks and Access to the Countryside Act 1949. The north-west boundary of the Chilterns is clearly defined by the escarpment. The dip slope is by definition more gradual and merges with the landscape to the south-east. The south-west endpoint is the River Thames. The hills decline slowly in prominence in north-east Bedfordshire.