The Diwan-i 'Am is a large pavilion for public imperial audiences at the center of the Red Fort. It is positioned between the public and private parts of the fortress. It faces a large open courtyard, and behind the back wall lie the private imperial palaces. The Diwan is a hypostyle hall in red sandstone, 9 bays wide and 3 bays deep. Each column has 12 sides, and supports cusped arches; this arch form, much used under Shah Jahah, has early Indian origins that can be traced to both Hindu and Buddhist sources. During Shah Jahan's time, the columns were plastered, painted and gilded, with rich cloths draped between them to create an opulent atmosphere. An ornate, canopied, throne-balcony for the emperor stands at the center of the eastern, back wall of the Diwan, behind which the private apartments lie. The throne balcony is of white marble, carved and inlayed with precious stones in pietra dura. A low bench in front of the throne seats a minister. Panels of pietra dura work depicting birds and flowers decorate the wall behind the throne; some of these were imported ready-made from Italy, while their settings are in a similar, but Mughal, technique.