… The peculiarity of Persian and Arabian architecture is the dome, which is called in Arabic the gunbad and the mehrab. Gunbad means dome, and mehrab means an arch used in windows and doors which is not exactly round, but is formed of three or five parts; in other words, in five half-circles with the top made by two lines going upward and joining in the center. The mystics of Arabia gave the interpretation of this form. They called it qasab-e kousein, which means “the meeting of the eyebrows”. When a person looks upward, naturally his eyebrows come closer to each other. The idea is that as the spirit soars upward, the tendency of the soul is to rise from duality to unity. By working with these two particular forms, they have arrived at such perfection that if the same form were continued for a hundred thousand years, one could never tire of it.
Excerpt from: Sufi Poetry and Lectures ~ by Hazrat Inayat Khan (r.a)