The vale is an extent of lower lying ground separating the chalk downs of
Salisbury Plain to the south from the
Marlborough Downs to the north. It is around long and around wide. At the western end is the town of Devizes. Larger settlements in the vale include
Pewsey and
Burbage with many smaller villages, the larger ones including
Bishops Cannings,
Etchilhampton,
Urchfont,
Chirton,
Alton Priors,
Woodborough,
Milton Lilbourne,
Easton Royal and
Wootton Rivers. Although not itself part of the
downs, the vale is included as part of the
North Wessex Downs AONB (
Area of Outstanding Natural Beauty). The vale is a major east–west feature opening to the west towards the
Bristol Channel, but is drained by the headwaters of the
Salisbury Avon, rather than the westward-flowing
Bristol Avon. The river cuts through the chalk scarp to the south at
Upavon and crosses Salisbury Plain towards the south coast. The higher part of the eastern vale south of Burbage is drained by the
River Bourne, which cuts the scarp at
Collingbourne Kingston, joining the Avon at
Salisbury. Since the area is not believed to have been glaciated, this probably indicates that the course of the rivers pre-dates the modern topography. The highest point is
Milk Hill (near
Alton Barnes) at 295 m / 968 ft above sea level, with the adjacent
Tan Hill summiting at 294 m / 965 ft. The vale is not used by any major roads, but is followed by a railway and canal as a route between the
London Basin and the west. To the north of Burbage the head of the Avon valley, draining west into the vale, meets the head of the
River Dun, draining east to the
Kennet and the
Thames. The valley floor at around above sea level provides a route through the downs which locally reach 200 to 300 metres. The
Kennet and Avon Canal and the
main line railway from London to the south-west make use of this route, the canal using the
Bruce Tunnel. Formerly another rail route between
Andover and
Marlborough also followed this gap. Another line formerly branched off towards
Bath via Devizes at the western end of the vale. ==Geology==