Shish Mahal or the Glass Palace is situated on the western side of the Muthamman Burj below the Diwan-i-Khas hall. Shah Jehan built it between 1631-40, perhaps to be used as imperial baths. Thus, it had extra thick walls to ensure cool interiors. It was so named because of the extensive use of mirrors in its walls and ceilings set in the plaster. It lent a beautiful dramatic effect when illuminated and thus, it was purposefully made dark to necessitate the use of artificial light. According to Abdul Hamid Lahauri, the historian of Shah Jehan, these splendid mirrors belonged to Haleb (Aleppo, Syria) that was the main centre for manufacturing such glasses at the time.
The palace consists of two large chambers connected through a broad arched opening in the center and two narrow passages on the sides. Only light that crept in here, reached here through the two doors and a ventilator in the southern wall. Both these chambers had a marble tank with fountains and arrangements for hot and cold water. The marble doors were provided so that the chamber could easily be used as the steam bath too. Besides the beautiful niches fitted with two inlets for water in the interior hall, there were two series of candle niches too, where the candles were kept to cast their reflection on the falling water casting a lovely effect.
The dado panels in the outer hall have inlaid borders with plants painted in the center. Black and red colors have been used abundantly. The stucco relief work in the panels above them depict ‘guldasta’ or bunch of flowers in combination with glass mosaic work and may have contained mirrors or beautiful portraits at some time. There is no inlay work on the dados in the inner hall but they have been dutifully painted to lend them the desired beauty. There are semi-soffits and the ceilings are ornamented with stalactite pattern. The chiseled stuccowork in conventional Persian motifs and designs adorn the ceiling of the entrance portal.