Alauddin Khilji, known for his strategic prowess, built the fortified city of Siri in response to Mongol invasions. Siri thrived with markets and palaces, leaving behind Alai Minar, Alai Darwaza, and the historic Hauz-e-Khas tank. Despite vanished structures, the era's cultural richness endures through figures like Amir Khusrau and Saint Nizamuddin. Read more on how Delhi was build.