The exterior decorations of Taj Mahal are among the finest to be found in Mughal architecture. As the surface area changes, a large pishtaq has more area than a smaller, the decorations are refined proportionally. The decorative elements were created by applying paint or stucco, or by stone inlays or by carvings. In line with the Islamic prohibition of the use of anthropomorphic forms, the decorative elements can be grouped into either calligraphy, abstract forms or vegetative motifs.
The calligraphy found in Taj Mahal are of florid thuluth script, created by
Persian calligrapher, Amanat Khan, who signed several of the panels. The calligraphy is made by jasper inlaid in white marble panels and the work found on the marble cenotaphs in the tomb is extremely detailed and delicate. Higher panels are written slightly larger to reduce skewing effect from viewing below. Throughout the complex, passages from the Qur'an are used as decorative elements. Recent scholarship suggests that Amanat Khan chose the passages as well. The texts refer to themes of judgment and include: Surah 91 - The Sun, Surah 112 - The Purity of Faith, Surah 89 - Daybreak, Surah 93 - Morning Light, Surah 95 - The Fig, Surah 94 - The Solace, Surah 36 - Ya Sin, Surah 81 - The Folding Up, Surah 82 - The Cleaving Asunder, Surah 84 - The Rending Asunder, Surah 98 - The Evidence, Surah 67 - Dominion, Surah 48 - Victory, Surah 77 - Those Sent Forth and Surah 39 - The Crowds. As one enters through Taj Mahal Gate, the calligraphy reads "O Soul, thou art at rest. Return to the Lord at peace with Him, and He at peace with you."
Abstract forms are used especially in plinth, minarets, gateway, mosque, jawab, and to a lesser extent, on the surfaces of the tomb. The domes and vaults of sandstone buildings are worked with tracery of incised painting to create elaborate geometric forms. On most joining areas, herringbone inlays define the space between adjoining elements. White inlays are used in sandstone buildings and dark or black inlays on the white marbles. Mortared areas of marble buildings have been stained or painted dark and thus creating a geometric patterns of considerable complexity. Floors and walkways use contrasting tiles or blocks in tessellation patterns.
Vegetative motifs are found at the lower walls of the tomb.
They are white marble dados that have been sculpted with realistic bas relief depictions of flowers and vines. The marble has been polished to emphasise exquisite detailing of these carvings. The dado frames and archway spandrels have been decorated with pietra dura inlays of highly stylised, almost geometric vines, flowers and fruits. The inlay stones are yellow marble, jasper and jade, leveled and polished to the surface of the walls.