The Nila Gumbad, the earliest Mughal era structure in Delhi, is so called on account of the blue (Nila) tiles that cover the dome. The tiles had mostly come loose and a large patch was missing with fragments falling off due to continued vibrations from the adjoining railway lines and during thunderstorms. In keeping with the philosophy adopted during the restoration of tiles at Humayun’s Tomb, no existing tile was removed from the dome even where these had lost their glaze.
The restoration of the tiles ensures long term protection and preservation of the tiles on the dome and the neck. The tile, besides restoring the appearance, also ensures preservation as they form a protective layer. In the neck of the dome are eight vaulted openings where grooves holding sandstone lattice screens as is typical were still visible. These screens seem to have been removed in the 20th century, thus allowing free access to birds besides also altered the original character of the structure. All the 8 sandstone lattice screens on the neck of the dome and 4 lattice screens on the lower level are restored.