The Alai Darwaza is the main gateway from southern side of the Quwwat-ul-Islam Mosque. It was built by the second Khilji Sultan of Delhi, Ala-ud-din Khilji in 1311 AD, who also added a court to the pillared to the eastern side. The domed gateway is decorated with red sandstone and inlaid white marble decorations, inscriptions in Naskh script, latticed stone screens and showcases the remarkable craftsmanship of the Turkic artisans who worked on it. This is the first building in India to employ Islamic architecture principles in its construction and ornamentation.
The Slave dynasty did not employ true Islamic architecture styles and used false domes and false arches. This makes the Alai Darwaza, the earliest example of first true arches and true domes in India. It is considered to be one of the most important buildings built in the Delhi sultanate period. With its pointed arches and spearhead of fringes, identified as lotus buds, it adds grace to the Quwwat-ul-Islam mosque to which it served as an entrance.