Geography of Dorset is the Blackmore Vale, a relatively low-lying area of clays and limestones of Jurassic age. The south-east of the county forms part of the Hampshire Basin, an asymmetric syncline covered in sands and gravels of Paleogene age. The main rivers in the county are the Stour, Frome and Piddle. The Stour is the county's largest river, although its source is in the neighbouring county of Wiltshire. The Frome and Piddle both lie wholly within the county. The whole of Dorset's coastline is designated part of the Jurassic Coast World Heritage Site, and contains examples of many different coastal landforms, reflecting
World Heritage Site Movement" (Argentina, Belgium, France, Germany, India, Japan, Switzerland) is a trans-regional property with component sites located in three regions - Europe and North America, Asia and the Pacific, and Latin America and the Caribbean. It is counted here in Europe and North America. Countries with fifteen or more World Heritage Sites, as of July 2018. Despite the successes of World Heritage listing in promoting conservation, the UNESCO administered project has attracted criticism from some for perceived under-representation of heritage sites outside Europe, disputed decisions on site selection and adverse impact of mass tourism on sites unable to manage rapid growth