Long before trucks climbed Bhote Koshi valley, mule caravans carried rice and other grain from Nepal north to Gyirong, where traders exchanged them for Tibetan salt and wool. Salt, highly valued in Nepal’s middle hills, travelled farther south towards India. Newar merchant communities also settled in Tibetan trading towns. Nepalese troops later used the route during invasions of Tibet in 1788 and 1791 before Chinese and Tibetan forces counter-attacked in 1792.

Source: Nepal flood: For centuries, flood-hit corridor was key route of Himalayan trade