Severn estuary. Truecolour satellite image of the estuary of the River Severn, bordered by southwest England (at right) and southeast Wales (at left). North is at top. The cities of Bristol (at lower right) and Cardiff (lower centre left) are seen, as are the towns of Newport (at lower centre) and Gloucester (at upper right). The valleys in the hills north of Cardiff contain urban areas. Agricultural areas appear as a patchwork of fields in the lowlands. The estuary has two major bridges crossing it (at lower centre). The Severn is Britains longest river, being about 338 kilometres long. The data for this image was gathered by the Landsat5 satellite.