The Cambridge History of India, Vol. I: Ancient India v1.c15.127

v1.c15.127

The other route of invasion lies five hundred miles away to the west and south-west. There the Afghān mountains come suddenly to an end, and an easy way lies round their fringe for four hundred miles over the open plateau, from Herāt to Kandahār. This way passes not far from Seistān. South-eastward of Kandahār it descends through a mountainous district into the lowland of the Indus. This is now called the Bolān route, from the last gorge towards India; but in ancient times the road went farther south over the Mūla Pass. It debouches upon the plain opposite to the great Indian desert. Therefore the Khyber route has been the more frequently trodden, for it leads directly, between the desert and the mountains, upon the Delhi gateway of inner India.