That would be interesting to know. I mainly base my conjectures on the McQuarrie artwork that shows monolithic stones:
JEDIT: I found the part in The Making of Star Wars which discusses it on page 45:
McQuarrie: “We (Lucas and McQuarrie) had quite a thorough idea of what it was like. To me it was really one of these seven wonders of the galaxy, a pile of giant disks that were so dense that you almost had the feeling that there was less gravity inside this thing. It wasn’t fully a real place.”
There’s more on page 263 when it comes to translating it to the McQuarrie art to the matte painting:
“I had done squares, almost Mayan-like. I put it together, showed it to George…and he sat there in dead silence, which means he doesn’t like something. Then he said, ‘Would it be possible to make it look more like Ralph’s?’ So I went back and repainted it to make it look exactly like Ralph’s painting.”
I assume by ‘squares’, he means that he had broken up the solid stone disks into smaller stone pieces as more of an architectural structure rather than a monumental one.