 With the only entrance a narrow valley between the peaks of Hiunchuli and Machapuchare, where run-off from glaciers drain into Modi Khola River, the Sanctuary was not penetrated by outsiders until 1956.Because of high mountains on all sides, the Annapurna Sanctuary receives only 7 hours of sunlight a day at the height of summer.The unique combination of heights and depths on the 5-7 day trek into the Annapurna Sanctuary give rise to an extraordinary variety of ecosystems.