Sri yantra is called the mother of all yantras because all other yantras derive from it.
The Sri Yantra is a configuration of nine interlacing triangles centered around the bindu (the central point of the yantra), drawn by the super imposition of five downward pointing triangles, representing Shakti ; the female principle and four upright triangles, representing Shiva ; the male principle.
Man's spiritual journey from the stage of material existence to ultimate enlightenment is mapped on the Sri Yantra. The spiritual journey is taken as a pilgrimage in which every step is an ascent to the center, a movement beyond one's limited existence, and every level is nearer to the goal.
Each of the circuits of the Sri Yantra, from the outer plane to the bindu (the center), corresponds with one of the stages of the spiritual journey.
The goal of contemplating the Sri Yantra is that the adept can rediscover his primordial sources. The circuits symbolically indicate the successive phases in the process of becoming.