The Suru and Zanskar valleys form a great trough enclosed by the Himalayas and the Zanskar Range. Rangdum is the highest inhabited region in the Suru valley, after which the valley rises to at Pensi-la, the gateway to Zanskar. Kargil, the only town in the Suru valley, is the second most important town in Ladakh. It was an important staging post on the routes of the trade caravans before 1947, being more or less equidistant, at about 230 kilometres from Srinagar, Leh, Skardu and Padum. The Zangskar valley lies in the troughs of the Stod and the Lungnak rivers. The region experiences heavy snowfall; the Pensi-la is open only between June and mid-October. Dras and the Mushkoh Valley form the western extremity of Ladakh.