It is characterised by a wide, flat, clay floodplain of the upper reaches of the Bristol Avon river, which divides the Cotswolds to the west from the chalk downland of east and south Wiltshire. It is triangular in shape with its north edge running from the town of Royal Wootton Bassett in the east to Malmesbury in the west. This prominent north ridge is the setting for the village of Brinkworth, which at five miles long, claims to be the longest village in England.