High Quality Content by WIKIPEDIA articles! The Aletsch Glacier (German: Aletschgletscher) or Great Aletsch Glacier (German: Grosser Aletschgletscher) is the largest glacier in the Alps. It has a length of about 23 km (14 mi) and covers more than 120 square kilometres (46 sq mi) in the eastern Bernese Alps in the Swiss canton of Valais. The Aletsch Glacier is composed of three smaller glaciers converging at Concordia, where its thickness is estimated to be near 1 km (3,300 ft). It then continues towards the Rhone valley before giving birth to the Massa River.