Old fort or Purana Qila was built by the second Mughal Emperor Humayun in 1533. Humayun wanted to establish a city of his own and so he chose Indraprastha for building the city. It took almost five years to build the Qila. Later Sher Shah overthrew him and took control over the city. The walls of the Fort rise to a height of 18 metres which are huge, and run on for about 1.5km. It has three arched gateways; facing West is the Bara Darwaza (Big Gate), south gate is the 'Humayun Gate' and lastly, the 'Talaqi Gate' or the forbidden gate. A true example of Mughal architecture.