Aar is a large Swiss river about 200 miles long, which falls into the Rhine as it leaves Switzerland. It is also the longest river located entirely within Switzerland.
It begins with melt from the Aare Glacier in Bern canton and flows north past Meiringen, through Aare Gorge, and into the glacial Lake Brienz. The river forms a canal as it enters Lake Thun, then forms an entrenched valley which circles the medieval region of Bern. It flows west into Lake Biel and northeast along the foot of the Jura Mountains, and is joined by the Reuss and Limmat rivers before being tribute to the Rhine.