The Sindh Sagar Doab is the largest of the five and the driest, running from the Salt Range down to the Thal desert, holding Rawalpindi, Attock, Mianwali, Khushab and Bhakkar.
Its northern part is the Pothohar plateau, broken country of ravines and loess, farmed on rain rather than canal. It is Punjabi-speaking in a distinct dialect and was the single heaviest army recruiting ground in British Punjab.
Rohtas fort, Katas Raj, Taxila and the Khewra salt mines are all in this doab. Khewra is the second largest salt mine in the world and has been worked since at least the Mughal period.
The Thal, the desert in its southern half, was irrigated only after 1947 by the Thal canal.
The March 1947 killings in Rawalpindi division took place here. The families displaced from it are the Pothoharis of Indian Punjab, and their dialect and their food are still distinguishable in Ludhiana and Delhi.
The loess of the plateau cuts into deep gullies once the grass cover goes, and the whole northern tract has a soil erosion problem that predates any modern argument about land use.
The Thal Canal, built from the 1940s, irrigated part of it and made a new colony belt in what had been sand.
The Indus runs along its western edge and the crossings at Attock and Kalabagh are where the doab ends. Everything that came into India from the north west entered along that edge.