Salisbury Plain is a chalk plateau in the south western part of central southern England covering . It is part of a system of chalk downlands throughout eastern and southern England formed by the rocks of the Chalk Group and largely lies within the county of Wiltshire, but stretches into Hampshire.
The plain is famous for its rich archaeology, including Stonehenge, one of England's best known landmarks. Large areas are given over to military training and thus the sparsely populated plain is the biggest remaining area of calcareous grassland in northwest Europe. Additionally the plain has arable land, and a few small areas of beech trees and coniferous woodland. Its highest point is Easton Hill.
The boundaries of Salisbury Plain have never been truly defined, and there is some difference of opinion as to its exact area. The river valleys surrounding it, and other downs and plains beyond them loosely define its boundaries. To the north the scarp of the downs overlooks the Vale of Pewsey, and to the northwest the Bristol Avon. The River Wylye runs along the southwest, and the Bourne runs to the east. The Hampshire Avon runs through the eastern half of the plain, and to the south the plain peters out as the river valleys close together before meeting at Salisbury. From here the Avon continues south to the English Channel at Christchurch. The Hampshire Downs and the Berkshire Downs are chalk downland to the east and north of Salisbury Plain, and the Dorset Downs and Cranborne Chase are to the southwest. In the west and north west the geology is mainly the clays and limestones of the Blackmore Vale, Avon Vale and Vale of Wardour. The Mendip Hills rise to the west of Salisbury Plain, and the Cotswolds to the north west.
Amesbury is considered the largest settlement on the plain (southern fringes), though there are a number of small villages, such as Tilshead, Chitterne and Shrewton in the middle of the plain, as well as various hamlets and army camps. The A303 road runs through the southern area of the plain, while the A345 and the A360 cut across the centre.