The Diwan-i-Aam, or Audience Hall, is located in Delhi's Red Fort. It was here that Mughal emperor Shah Jahan (best known for building the Taj Mahal) and his successors meet with citizens to hear their grievances and requests.
The Audience Hall is covered with a roof but is open on three sides, with a back wall and weight-bearing pillars and arches made of red sandstone. The hall measures 100 x 60 feet. Apparently at one time its ceiling and columns were painted with gold -- that would have been quite a sight.
It's an impressive and beautifully constructed space, highlighted by place where the Emperor would sit -- a magnificent elevated white marble throne inlaid with semi-precious stone (a technique later perfected in the Taj Mahal). Today the throne is unapproachable, sitting behind a protective transparent barrier.
The entire complex, for obvious reasons, is a UNESCO World Heritage site.