Cornwall has an area of 354,628 hectares and is the second largest county in the region in terms of area but has a relatively low population density. Cornwall comprises the westernmost part of the southwest peninsula, and has an estimated 697 kilometres of coastline including the lower reaches of the main estuaries, the longest of any English county. The sea forms the northern, southern and western boundaries. To the east, Cornwall's border with Devon is formed by the River Tamar, which forms a physical and cultural divide with the rest of Great Britain, for all but 18 km of its length. The Isles of Scilly lie 45 km off Lands End.  The nearest major centre outside the county, Plymouth, is 125 km from Penzance, while Bristol, the regional centre, is 290 km from Penzance, with London 450 km away. The distance between the north and south coasts varies from 72 km at the eastern boundary to as little as 8 km at the western end of the county between Hayle and Marazion. In length Cornwall measures a maximum of 132 km between Lands End and the northeastern boundary at Morwenstow.  Despite a past history of mining, tourism has gradually developed into one of the major industries and there has been some more recent development of the manufacturing industry. Farming is still a key contributor to the local economy and agriculture is the predominant land use. In more recent times Cornwall has seen developments in its renewable energy sector and knowledge economy led, in part, by the creation of the new Combined Universities in Cornwall. The fishing and marine industries contribute greatly to the character of Cornwall.