Aligarh is the 22nd largest Hindi speaking city of India with a total population of over 8,70,000. Highest employment in Aligarh district is in Agriculture, manufacture of locks and in the Hardware industry. Aligarh has 47% Agricultural workers, 46% workers in Industry and other services and 7% Household workers. Aligarh is a good agricultural belt because of the proximity to both the Ganga and Yamuna Rivers. The entire Aligarh district falls in the Upper Ganga Doab region represented by flat topography. The irrigation in the district takes place through the Upper and Lower Ganga Canal network system. Before the 18th century, Aligarh was known as Kol. Statues of Buddha and other Buddhist remains have been found in excavations where the citadel of Kol stood, indicating a Buddhist influence. In 1194, Qutb-ud-din Aibak marched from Delhi to Kol, to "one of the most celebrated fortresses of Hind". Qutb-ud-din Aibak appointed Hisam-ud-din Ulbak as the first Muslim governor of Kol. Kol is mentioned in Ibn Battutas Rihla, when Ibn Battuta along with 15 ambassadors representing Ukhaantu Khan, the emperor of the Mongol Chinese Yuan dynasty, travelled through Kol city to the coast of Cambay (in Gujarat) in 1341. In 1804, the Aligarh district was formed by the union of the second, third and fourth British divisions with the addition of Anupshahr from Moradabad and Sikandra Rao from Etawa. Aligarh Muslim University is the prominent educational center of Aligarh.