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
Mining in Cornwall and Devon World Heritage list. It was announced on 13 July 2006 that the bid had been successful. This World Heritage Site is unique in that it covers a technique exported worldwide, including Mexico and Peru, and will consist of a trail linking mining sites from Land's End in Cornwall, through Porthtowan and St Agnes up the spine of the county to the Tamar Valley forming the border with Devon. There, the exporting port of Morwellham is being developed alongside the Devon Great Consols Mine to demonstrate the nature and scale of the operations, with the Eastern Gateway to the World Heritage