Akbar did not erect any permanent building for holding his Public Audience Diwan-i-Am or Private Audience (Diwan-i-Khas) though both these Mughal institutions were founded by Emperor Akbar. The Sultans of Delhi had only one such institution Bar-i-Am or Bargah. During the reign of Emperor Akbar the function of the Audience was held in temporary wooden structures added with shamiyana in Agra Fort. This arrangement continued during the reign of Jahangir (c.1605-1628). On 14th February 1628, Shah Jahan issued an order that halls for his public audiences should be constructed in all the great-fortified forts (palaces) of the capitals of the Mughal Empire, particularly at Agra and Lahore.
These halls were first built in wood (Iwan-i-Chobin) which were later replaced by larger structures, painted with marble plaster.
Shah Jahan's historians and poets described the Audience Hall as Iwan-i-Daulat Khana-wa-Khass-o-Am or Hall of Public Audiences and Iwan-i-Chehil Sutun of Forty-pillared Hall, which is now called Diwan-i-Am.
The Diwan-i-Am is built in red sandstone on a raised platform (1.25 m) in a rectangular plan measuring 61.77 m by 20.12 m. The total large pillars are 48 but if the corner ones are omitted, these are 40 long pillars over which the engrailed arches support the flat stone roof.
The Hall is opened in three sides with multi foiled arches except the eastern side with the structure of the jharokha contained the celebrated throne Takht-i-Murassa which was occupied by the Emperor for giving public audiences in the forenoon. Few attempts have been made to integrate the information contained in literary and visual sources with what can be derived from the architecture itself. The reason given by the Court historians for the construction of the Diwan-i-Am, namely to protect the Emperor's Khassan from the vicissitudes of the weather.
It is Abu Salih Kanbo who tells us about Shah Jahan's Audience Halls. Kanbo describes both the wooden hall of Agra and the stone hall of Delhi which he describes as Iwan-i-Chehil Sutun (forty pillared state hall), Diwan-kada-i-adl-o-dad (court house of Equity and Justice) and Bargah-i-Sulaimani with several famous legendary and historical palaces of the past, in particular with the Iwan-i-Nushirmwan and the Bargah-i-Sulaiman.
Shah Jahan's Chehil Sutun in the courtyards of Khass-wa-Am acquired their greatest splendour during the yearly Nawruz celebrations of the Mughal Court. All three Audience Halls follow exactly the same scheme, but they are not all the same size. The biggest Hall is that of Agra, those of Lahore and Delhi are smaller and close to each other in their dimensions. Each of the Diwan-i-Ams shows the same flat roofed hypostile construction erected on a grid pattern.
The twenty-seven bays are demarcated by covered ceilings (chashma) set off by multi foiled arches (taq-i-marghuldar) and large twelve-sided "Shah Jahani" columns. The columns are paired on the outer sides, which produce a quadruple formation in the corners. Each hall thus has forty-eight full columns and twelve half columns.
In addition to being the Administrative Centre of the Mughal Empire the Diwan-i-Am, provided a stage for the great court festivals, in particular Nawruz (the Persian New year Day) and Julus (the accession anniversary). It was also the setting for such state ceremonies as weighing the Emperor and Princesses on his solar and lunar birthdays (jashn-i-Wazn-i-shamsi, jashn-i-Wazn-i-qamari). When the royal princesses wedding was held the Diwan-i-Am was sometimes called Khalwat ("seclusion" or "retirement"), because on those occasions men had to evacuate the courtyard to allow the Imperial women to use the Diwan-i-Am as an exhibition hall where they arranged the dowry and the wedding presents for display during a public audience by the Emperor to the court. The Audience Hall also played a part in the celebration religious festivals such as 'Id'. The Emperor feasted scholars and pious persons with a banquet there on the Milad (the Prophets Birthday). During the whole month of Ramadhan, fast breaking meals (iftar) would be given to the deserving poor at Imperial expense. The Emperor also used it to receive foreign dignitaries and delegations. The Hindu festivals were also celebrated at the Diwan-i-Am as is evidenced from a contemporary painting of Emperor Jahangir celebrating Holi at Diwan-i-Am at Agra. The painting made by Govardhan is preserved in the Rampur Raza Library collection.
All in all, the Diwan-i-Am was the centre of Court events and Mughal rule where the power and pomp of the grand Mughal were enacted.
The silver balustrades were set up originally for the Mughal nobles to stand in front of the Emperor according to their mansabs (ranks). Those who held the rank, more than five to ten thousand, stood near the Jharoka of the Emperor. The lower ranks stood behind these nobles. The officers holding ranks lower than 200 in the numerical hierarchy did not stand in the Diwan-i-Am hall but in the red sandstone arched galleries that stood near the Chehil Sutun Hall. The silver and wooden railings were fixed in the hall for different ranks of nobles attending the Darbar. The Hall and its demarcated areas inside were embellished with fine European brocades and Iranian carpets which added lustre to the Diwan-i-Am and created awe in the hearts of the nobles and the public who visited for redressal of their grievances.
There is a rectangular marble dice with four foots in the Diwan-i-Am in front of the Jharoka where the Prime Minister used to stand and submit the grievance applications of the public to the Emperor for consideration.
The Diwan-i-Am is backed on the east by a wall in the middle of which is the throne chamber, an alcove of richly inlaid marble with a trefoil arched ornate facade. The arch is finely decorated with pietra dura works. This chamber is connected with the Machhi Bhawan on the east, while from the Diwan-i-Am a flight of steps leads to Machhi Bhawan and further on the palaces where from the royal ladies had viewed certain ceremonies of the Diwan-i-Am through the perforated screens of the marble windows on the right and left sides of the alcove.