A fiord is formed where the sea enters a deeply excavated glacial trough after the melting-away of the ice, one of the finest fiords being Milford Sound. The thickness of the ice that excavated the basin is shown by the height of the subvertical cliffs that rise from below sealevel, to truncate the U-shaped profiles of older glacial valleys. These ’hanging’ valleys are particularly noticeable in the area, such as Sinbad Gulley, on the right of Mitre Peak. Where once smaller glaciers served as tributaries to the main iceflow, streams now run and enter the principal valley as waterfalls.