The construction materials that were used to build the Taj Mahal consisted of marbles, precious gemstones and other things, all of which were transported with the help of over 1,000 elephants.
If you look closely, you can see calligraphic inscriptions of ninety-nine names of Allah on the tomb of Mumtaz Mahal.
The head architect for the Taj Mahal was Ustad Ahmad Lahori, who was an amputee.
The construction of Taj Mahal was done in a way such that the minarets all tilt a little outwards, as a means to protect the dome during natural disasters such as earthquakes.
Since the Islamic scriptures forbid any decorations or inscriptions on the tomb, the room in which the tombs of Mumtaz Mahal and Shah Jahan are located, does not have any decorative work or detailing in the walls.