Definitely there is a falling water table. Originally, there supposedly were 2 different Taj Mahals planned (White and Black), with the black across the river and connected with a bridge, but the rive can be walked/wades now. There appears to be remnants of the foundation construction of the second, but the Shah was committed by his son.
The existing Taj is a monument to symmetry, with identical semi-precious gems ground in pair were adhered to the marble on opposite ends of the faces of the structure. The exceptions are minor, like the width of the inlays increasing slightly from bottom to top.
A major variation (I did not measure) is the tilt of the minarets or towers that tilt out very slightly, so if there was a collapse/failure, the tower should fall away from the central portion and not on the tombs or crypts. An eventual collapse was anticipated.
Because of the age, the details make sense, but the physical design and details are not available.
I am just an engineer with a lot of international travel and not a tourist, but this building is amazing and unique and it is head and shoulders above others I have seen.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.