In the medieval period, Ilaq lay along the valley of the Angren River, to the north of the large bend of the Syr Darya near Khujand. The district, which was composed of a mixed terrain of plains and mountains, was bounded on the west by the Syr Darya and on the north by the region of Shash (modern Tashkent), and it extended to the western edge of the Tian Shan in the east. Due to the proximity of Shash and Ilaq, the two districts were sometimes linked by Muslim geographers, who either treated them as one united area or characterized Ilaq as a dependency of Shash. As a combined unit, Shash-Ilaq constituted one of the five primary sedentary regions of pre-modern Central Asia, along with Sughd, Khwarazm, Farghana, and the area of Balkh.