The interior chamber of the Taj Mahal steps far beyond traditional decorative elements. Here, the inlay work is not pietra dura, but a lapidary of precious and semiprecious gemstones. The inner chamber is an octagon with the design allowing for entry from each face, although only the door facing the garden to the south is used.
The interior walls are about 25 metres (82 ft) high and are topped by a "false" interior dome decorated with a sun motif. Eight pishtaq arches define the space at ground level and, as with the exterior, each lower pishtaq is crowned by a second pishtaq about midway up the wall. The four central upper arches form balconies or viewing areas, and each balcony's exterior window has an intricate screen or jali cut from marble. In addition to the light from the balcony screens, light enters through roof openings covered by chattris at the corners. Each chamber wall has been highly decorated with dado bas-relief, intricate lapidary inlay and refined calligraphy panels, reflecting in miniature detail the design elements seen throughout the exterior of the complex.
The octagonal marble screen or jali which borders the cenotaphs is made from eight marble panels which have been carved through with intricate pierce work. The remaining surfaces have been inlaid in extremely delicate detail with semi-precious stones forming twining vines, fruits and flowers.
Muslim tradition forbids elaborate decoration of graves. Hence, the bodies of Mumtaz and Shah Jahan were put in a relatively plain crypt beneath the inner chamber with their faces turned right and towards Mecca. Mumtaz Mahal's cenotaph is placed at the precise center of the inner chamber on a rectangular marble base of 1.5 metres (4 ft 11 in) by 2.5 metres (8 ft 2 in).