The Shri Yantra is one of the most powerful and dynamic yantras. It appears to be symmetrical, but its center is made up of 9 intersecting triangles. 4 upward pointing triangles represent Shiva (the male principle) and 5 downward pointing triangles represent Shakti (the female principle). The imbalance in this yantra makes it more powerful. Together, the Shiva and Shakti encompass all of the cosmos.
Each triangle, groupings of triangles, and lotus petals correspond to the chakras and have powerful properties such as healing, protection, realization, luck, materialization of expectations, and desired objects.
All yantras have a balancing effect upon their creator. Both hemispheres of the brain are simultaneously used while creating yantras, which creates positive new pathways in the brain. The center of the Shri yantra (shown in this video) especially involves these mental and visual gymnastics!
For more information read “Tools for Tantra” by Harish Joahri.