The Slave rulers were succeeded by the Khiljis on the political scene of Delhi by the end of 13th Century. The Khiljis were, in fact, a Turkish tribe and settled in Afghanistan, where they acquired Afghani manners and customs. Among the six rulers of Khilji dynasty, Alauddin Khilji laid the foundation of his capital Siri in 1303 A.D. He also commissioned a minar (Victory Tower) exceeding the Qutab Minar but the same could not be completed. He also excavated a reservoir known as Hauz Khaz to meet the requirement of Siri township. He also constructed semi circular gateway with horseshoe shaped arch with lotus metifs. This gateway is popularly known as Alai Darwaja and has been considered, in the history of Islamic Architecture a representative of a true arch.