High Quality Content by WIKIPEDIA articles! Siri Fort, in the city of New Delhi, was built during the rule of Ala-ud-Din Khalji of the Delhi Sultanate to defend the city from the onslaught of the Mongols. It was the second of the seven cities of medieval Delhi built around 1303 (stated to be the first entirely constructed by Muslims), which at present is seen only in ruins with a few remnants (pictured)