Discuss the reasons and advantages of introducing the Double Dome feature in Indo-Islamic architecture.

The tomb of Sikandar Lodi was the first example with a double dome feature. The method of making double dome was originally practised in East Asia before it was imported into India.
A double dome has two layers and its objective was to lift the height of the monument and also keep its attraction intact. The problem with the single dome was that if it was erected very high, it left a deep void inside the building. If it was kept low, then it diminished the monumental effect of the building. In double dome, the dome instead of consisting of one thickness of masonry was composed of two separate shells-inner and outer with ample space between them.
The inside layer provides ceiling to the interior of the building, while the outer layer crowns the buildings. Use of two domes enables the ceiling inside to be placed lower and in better relation to the Interior space it covers. This is done without disturbing the proportions and the effect of elevation of the exterior.
The fully mature form of the double dome is seen, for the first time in India in the tomb of Humayun.