According to Natural England, who have designated the Weymouth Lowlands as National Character Area 138, they cover an area of 13,251 hectares; a coastal strip between about 1 and 6 kilometres wide, running from the Bride Valley, west of Burton Bradstock, to east of Osmington and including the town of Weymouth, the main settlement of the area. A steep ridge of chalk marks the start of the Dorset Downs to the north; to the south is the Isle of Portland and to the east is the Isle of Purbeck