Wales has a complex geological history which has left it a largely mountainous country. The coastal plain is narrow in the north and west of the country but wider in the south, where the Vale of Glamorgan has some of the best agricultural land. Exploitation of the South Wales Coalfield during the Industrial Revolution resulted in the development of an urban economy in the South Wales Valleys, and the expansion of the port cities of Newport, Cardiff and Swansea for the export of coal. The smaller North Wales Coalfield was also developed at this time, but elsewhere in the country, the landscape is rural and communities are small, the economy being largely dependent on agriculture and tourism. The climate is influenced by the proximity of the country to the Atlantic Ocean and the prevailing westerly winds; thus it tends to be mild, cloudy, wet and windy.