The center of that circle is a void. The 'stone' is an 'adornment' of a 'facade' of the 'empty' 'box'. It used to be full of idols, but then the Prophet (SAW) knocked them all into little pieces and swept that box clean of idolatry. Now this is what you need to picture in your mind: 5 revolving timezones continually sweep the globe. Any Muslim that find himself or herself in one of those timezones is prostrating towards that 'empty' 'box'. This happens all around the globe, and as the globe turns, different radials are activated and others deactivated. So there is this wonderful dynamic arrangement of souls bowing towards one another, each saying in their hearts (if they are indeed faithful) that "There is no god but God" while they prostrate towards one another. Now 'boxes' are very interesting. In Semitic languages 'box' and 'chest' and 'crib' and 'ark' are all derivatives of the same root letters. Now Noah (SAW) carried the chosen remnant in an 'ark', and then the Israelites carried the Commandments in a 'box' (Ark of Covenant), and then the "word of God" (Salaam is ever upon him) (you know who) spoke as a babe in a 'box' (Crib in the manger), and now here we are, in the final act, where sons and daughters of Adam (SAW) bow to one another arrayed in a living circle towards an 'empty box'. (You too have a 'box' that you carry with you and it is your 'chest' where this Spiritual organ called the Heart resides. Now, the thing to do is make sure your box is entirely empty and void of any idols just like the Box in Mecca.)