A wide deep valley flanked by lofty mountains extends from the N. wall for many miles towards the N.W. It is an especially noteworthy object when the W. wall of Santbech is on the evening terminator, as its somewhat winding course, indicated by the bright summit-ridges of the bordering mountains, can be followed some hours before either the interior of the valley or the region between it and Santbech are in sunlight.