Explanation:

 A double dome is built of two layers. There is one layer inside which provides ceiling to the interior of the building. The other layer is the outer one which crowns the buildings. The devices of double dome enable 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 method of making double dome was practiced In east Asia for quite some time before it was imported into India. It was a problem for the early Muslim builders to place a dome over an edifice effectively. If they erected it high, it left a deep void of darkness in the ceiling of the building it cover-ed. In case they kept it low. In proportion with the dimensions of the room. it diminished the monumental effect of the structure. The solution was invented as double dome. In this innovation. The dome. Instead of consisting of one thickness of masonry. Was composed of two separate shells—one Outer and the other inner-with ample space between them. The attempts in the direction of Double Dome started with tomb of Taj Khan (1501) and the tomb of Sikandar Lodi (1518), both in Delhi. However, the fully mature form of the double dome is seen, for the first time in the tomb of Humayun.