[3][4] The chalk escarpment of the Chiltern Hills overlooks the Vale of Aylesbury and roughly coincides with the southernmost extent of the ice sheet during the Anglian glacial maximum.

[citation needed] The Chilterns are part of a system of chalk downlands throughout eastern and southern England, formed between 65 and 95 million years ago,[3] comprising rocks of the Chalk Group; this also includes Salisbury Plain, Cranborne Chase, the Isle of Wight and the South Downs in the south.

The beds of the Chalk Group were deposited over the buried northwestern margin of the Anglo-Brabant Massif during the Late Cretaceous.

[6] The formation is thinner through the Chiltern Hills than the chalk strata to the north and south and deposition was tectonically controlled, with the Lilley Bottom structure playing a significant role at times.

The highest point is at 267 m (876 ft.) above sea level at Haddington Hill near Wendover in Buckinghamshire; a stone monument marks the summit.

The next most important, and archetypal, landscape form is woodland, covering 21% of the Chilterns, which is thus one of the most heavily wooded areas in England.

Other rivers arising near the Chilterns include the Mimram, the Ver, the Gade, the Bulbourne, the Chess, the Misbourne and the Wye.

These are classified as chalk streams, although the Lea is degraded by water from road drains and sewage treatment works.

Portions around Leighton Buzzard and Hitchin are drained by the Ouzel, the Flit and the Hiz, all of which ultimately flow into the River Great Ouse (the last two via the Ivel).

During the Iron Age, the Chiltern ridge provided a relatively safe and easily navigable route across southern Britain.

[14] Before the 18th century, the population lived dispersed across the largely rural landscape of the Chilterns in remote villages, hamlets, farmsteads, and market towns along the main turnpike routes which coursed through the navigable valleys.

In 1965 almost half of the Chiltern Hills was designated[citation needed] as an Area of Outstanding Natural Beauty (AONB).

Historically it was drawn from the aquifer via ponds, deep wells, occasional springs or bournes and chalk streams and rivers.

Today the chalk aquifer is exploited via a network of pumping stations to provide a public supply for domestic consumption, agriculture and business uses, both within and well-beyond the Chilterns area.

As people have come to appreciate the open country, the area has become a visitor destination and the National Trust has acquired land to preserve its character, for example at Ashridge, near Tring.

In places, with the reduction of sheep grazing, action has been taken to maintain open downland by suppressing the natural growth of scrub and birch woodland.

This open-air folk museum contains reconstructed buildings which might otherwise have been destroyed or demolished as a result of redevelopment or road construction.

[citation needed] Hills in The Chilterns National Landscape with more than 30 metres of topographic prominence are listed from southwest to northeast.