A full solar eclipse is what an architect would design if he could. The power of an eclipse comes from deep within a person. A person that has never experienced anything to judge it against. That giant fireball, that has been, just ... sitting up there, day after day forever, did something incredible. Actually it didn't, the sun had nothing to do with it... the moon was the hero...
The real beauty of the eclipse, is a geometrical one. Our star is 400x times larger, and 400x further away than our moon. Roughly, sort of... The mathematical margins of error we are dealing with are huge. Of course the limitations of the human eye mean it really doesn't matter. Our eye wouldn't know the difference between 90% and 95% when we're talking 92 million miles away. So we're close, and perfect enough.
The classical architectural relevance is clear: powerful form, positive and negative, all the right architectural notes. But the serendipity. The birds laying down and the insects waking up. Shadows so sharp the mind has trouble making sense of it. Stillness. There really is a feeling of awe that can't be described by someone who hasn't experienced it.
Great Architecture should makes us question, feel, and want more in the same way. The truly great spaces can't be calculated or anticipated fully. Spaces can only be set, like a stage, in the hopes that 92 million miles away, the Sun might drop that perfect shadow, the moon might rise in just the right spot, and there might just be one of us there to see it.