Taken from "Warriors of Legend - Reflections of Japan in Sailor Moon"
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In the manga version, the exterior of the shrine is shown as the same one as that of Azabu's Hikawa Shrine. The anime however uses the Hikawa shrine in Akasaka as its model.
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The book doesn't mention anything about the interior of the shire, but if the exterior were based on those two shrines, then the interior probably were as well.
Here's a link to the Akasaka Shrine official site:
http://www.akasakahikawa.or.jp/
And if you go to the end of this site:
http://www.akasakahikawa.or.jp/contents/index.html
I think you will find a floor plan of sorts. unfortunately it's in japanese, so I can't be certain.