In 1533 second Mughal Emperor began construction of a fortified city called Dinpanah, ‘the asylum of the faith’, the present day Old Fort or Puana Quila. Within a year the wall, gates and bastion were completed and city was fortified.
However the three main gates on the north, south and west are part of the fortifications of the Purana Qila, the sixth city of Delhi, built by Sher Shah Suri (1538–45). Sher Shah Suri raised his citadel after demolishing Dinpanah, the city built by Humayun. The fortifications of the Qila extended to a boundary of (2 km (1.2 mi)) on an irregularly oblong plan. Bastions adorned the corners and the western wall. All three gates are double–storied structures built with red sandstone and have chhatris.
The Purana Qila was stated to have been left unfinished by Suri, which was later completed by Humayun. The southern gate is called the Humayun Darwaza; the reasons attributed for the name are that either Humayun built it or the gate overlooked Humayun’s tomb. An inscription in ink on the gate refers to Sher Shah with the date as 950 A.H. (1543–44).