Riederalp is a municipality in the district of Raron in the canton of Valais in Switzerland. It was created in 2003 through the merger of Goppisberg, Greich and Ried-Mörel.

The Aletsch Glacier or Great Aletsch Glacier is the largest glacier in the Alps. It has a length of about 23 km (14 mi) (2014), a volume of 15.4 km3 (3.7 cu mi) (2011), and covers about 81.7 km2 (2011) in the eastern Bernese Alps in the Swiss canton of Valais. The Aletsch Glacier is composed of four smaller glaciers converging at Konkordiaplatz, where its thickness was measured by the ETH to be still near 1 km (3,300 ft). It then continues towards the Rhône valley before giving birth to the Massa. The Aletsch Glacier is – like most glaciers in the world today – a retreating glacier. As of 2016, since 1980 it lost 1.3 kilometres (0.81 mi) of its length, since 1870 3.2 kilometres (2.0 mi), and lost also more than 300 metres (980 ft) of its thickness.