Ardelan and Bakhtiar have pointed out the significance of the Dome as a mandala which, in the Islamic and Sufic perspective relates to the Dimensions of the Universe, the archetypes of the Divine Names and Qualities.
When the Prophet described his ascent to heaven he spoke of an immense mother of pearl dome resting on a square with four corner pillars on which was written the four-part Quranic formula "In the Name - of God - the Compassionate - and the Merciful". The dome rested upon a square, held apart by an octagon which symbolised the eight angels.
The illustration above shows part of the dome of the Darb-e-Imam built in 1453. Note the elaborate geometry which expands the point from which the sanctuary lamp hangs into a circle and then reduces the circle to the square structure of the sanctuary through a sixteen sided polygon and thence through an octagon of eight squinches. Note too how the squinches on the corners are reduced into the walls through a series of hanging pendentives.