The valley extends about from the Lötschenlücke (3178 m) at the top of the Langgletscher to the mouth of the valley at Steg/Gampel (630 m). It is surrounded by 3,000 meter high mountains, including the Bietschhorn (3,934 m), the Hockenhorn (3,293 m), the Wilerhorn (3,307 m) and the Petersgrat (3,205 m). The Jungfrau-Aletsch Protected Area is the most glaciated area in the Swiss Alps, and was declared a Natural World Heritage Site by decision of UNESCO on December 13, 2001, along with southern and eastern parts of the Lötschental.