The Outer Sanctuary occupies the western third of the total sanctuary, and is separated from the Inner Sanctuary by high ridges, through which flows the Rishi Ganga. It is split in two by the Rishi Ganga; on the north side lies the Ramani Glacier, flowing down from the slopes of Dunagiri and Changabang, and on the south lies the Trisul Glacier, flowing from the peak of the same name. This portion of the sanctuary is accessible to the outside (though requiring the crossing of a pass). The first serious climbing expedition to pass through the Outer Sanctuary was that of T. G. Longstaff, who climbed Trisul I in 1907 via the eponymous glacier.