The Chiltern Hills, an Area of Outstanding Natural Beauty, occupy the south of the county and contain its highest point, Haddington Hill (). The Chilterns are the source of the River Ouzel, which flows across the lowland Vale of Aylesbury in the north of the county and through Milton Keynes before meeting the River Great Ouse at Newport Pagnell. The Thames forms part of the county's southern boundary.
The Chiltern Hills an Area of Outstanding Natural Beauty, occupy the south of the county and contain its highest point, Haddington Hill (). The Chilterns are the source of the River Ouzel, which flows across the lowland Vale of Aylesbury in the north of the county and through Milton Keynes before meeting the River Great Ouse at, Newport Pagnell. The Thames forms part of the county's southern boundary.