The Basement Chambers and a probable Third Grave at Taj
Two staircases on the northern side of the red sandstone plinth of the Taj Mahal lead below into the basement chambers which are seventeen in number and have been laid out in a line on the riverside of a narrow through-corridor. The rooms and corridor are of arcuate construction in brick and plaster, with stucco and painting ornamentation, distributed aesthetically on the soffits. At the extreme points on both sides of Taj Mahal there are doors sunk in the northern wall. They were blocked up permanently and securely with thick masonry at some unknown date, undoubtedly for some well calculated purpose. As may be surmised, the set on the northern side could have been repeated on the sides below the marble structure, with a rotating corridor, chambers and probably a crypt in the centre - all being interconnected.
This crypt would have contained the third and the real set of graves. The custom of providing cenotaphs or replicas had been followed by the Turks and the Mughals alike as we meet with this practice at the tomb of Iltutmish at Delhi and at the tombs of Saqid Khan and Akbar at Agra. The tomb of Akbar has three tombstones, one on the grave and two as cenotaphs. The tomb of Itmad-ud-Dauhlah and Chini-ka-Rauza too had three tombstones each. The lowest of the former was contained in a crypt which was originally accessible from the riverside and has now been completely blocked up. These examples indicate that the Mughals liked to provide three tombstones in a mausoleum.
At the Taj Mahal, the third is traditionally claimed to exist. It is only in these underground vaults that the third set could have been placed. The doors in the basement corridor no doubt exist and must have originally given entry to some underground arrangement of chambers and corridors. Though they are now impregnably blocked, their existence lends weight to the legendary version.