The Aar (German Aare) is the longest river that both rises and ends entirely within Switzerland. Bridgwater, W. & Beatrice Aldrich. (1966) The Columbia-Viking Desk Encyclopedia. Columbia University. p. 11.

Its total length from its source to its junction with the Rhine comprises about 295 km (183 miles), during which distance it descends 1,565 m (5,135 ft), draining an area of 17,779 km² (6,865 mi²) "Aare River." Encyclopædia Britannica. 9 Jan. 2007 .