why do we circumambulate?

oftentimes before going to pray at the Shrines, we circumambulate in silence and reverence, before going inside. recently, I've had the conversation with some friends asking why this is the case - why do we circumambulate? what is its significance?

according to wikipedia: Circumambulation is the act of moving around a sacred object. reading the following quote might give a nudge in the right direction:

The spiritual world is like unto the phenomenal world. They are the exact counterpart of each other. Whatever objects appear in this world of existence are the outer pictures of the world of heaven. (Abdu'l-Baha, The Promulgation of Universal Peace, p. 9)

so what would be the spiritual equivalent of circumambulation? maybe it could have to do with the fact that when we circumambulate in the physical world, our center of attention is the Shrine and the Manifestation of God, and a reminder that we should try to do the same in the spiritual world:

The state of prayer is the best of conditions, for man is then associating with God. (Abdu'l-Baha, Selections from the Writings of Abdu'l-Baha, p. 201)

so in the same way that our physical bodies center around the physical remains of the Manifestation of God when we circumambulate, we should try to have our soul and thoughts constantly centered on the Manifestation, His life and teachings.

how to do that is another subject altogether...