Dhaulagiri and Annapurna are apart on either side of the gorge of the Kali Gandaki river, a tributary of the Ganges. As the expedition approached from the south Dhaulagiri was clearly visible as a white pyramid to the west whereas Annapurna to the east was hidden behind the Nilgiri mountains. On first seeing Dhaulagiri on 17 April the immediate impression was that it was unclimbable. They could not see Annapurna but there was a break in the Nilgiris where the Miristi Kola flows into the Kali Gandaki through a deep and narrow gorge with an impenetrable entrance. The 1920s Survey of India map they were using (see left-hand Annapurna map below) showed a path leading up the gorge and over Tilicho Pass that might provide a route to the north face of Annapurna. However, none of the local inhabitants they spoke to knew of a path or had any further information. Continuing up the Kali Gandaki Gorge the team reached the market town of Tukusha at on 21 April. The people lived there in primitive conditions - Terray described the place as having biblical charm. Couzy climbed a Nilgiri peak to the east of Tukusha to inspect the eastern Dhaulagiri terrain and he concluded the southeast ridge was absolutely frightful. Even so, Herzog decided that they should first focus on Dhaulagiri, the higher mountain, since they would only have to investigate possible routes to the summit and would not have to reconnoitre to find the mountain itself.