Regarding the Dome of the Rock in Jerusalem; I once heard a student of Keith Kritchlow, who's a professor here in England in Sacred Architecture. And I heard this professor give a lecture, and he said, "It is almost a perfect design, but there's only one problem. It's lacking the intermediary piece."

And what he said is, the Dome represents Heaven, and the Octoganal base represents Earth. But there is not an intermediary piece, and in Architecture, this is something that is lacking, because we always need that intermediary piece and you'll see this in many sacred structures; A third piece.

I went up to him, and this is Ilham, Alhamdullilah.  I went up to him, after the lecture and said, "with all respect to your knowledge, I'm not an architect, and my knowledge is very little in this field. But you are mistaken; There is a reason why they left out that piece."

And he said, "what is that?"

And I said, this represents the meeting of Heaven and Earth, without intermediary, because this represents the meeting that the Prophet (SAWS) had with his Lord, without the mediation of Gabriel, and he just he literally He just said, "Wow". Which is the way non-Muslims say Subhanallah.

- Shaikh Hamza Yusuf ( The Concept of Jihad in Islam )