Besides being inspired by Metropolis, German Expressionism and Fascist Architecture, I recall the production designers mentioning a specific designer (possibly Japanese) who inspired them for the large vents installed in the Flugelheim Museum. I'd love to see more of that artist / architects designs.
Okay, I just found it in an article. His name is Shin Takamatsu. Looking at his unique architectural designs you can clearly see Anton Furst paying his homage to the man.
Here is his homepage: http://www.takamatsu.co.jp/_eng/index.php (http://www.takamatsu.co.jp/_eng/index.php)
His older projects (found on Google) perfectly reflect what we now see as the Gotham look.
Considering that Anton Furst is credited for the Art Deco production, I think you'll find a lot of his work easily.
I found this photo containing a caption of a Japanese dental clinic as an influence of the Flugelheim Museum's design.
(https://www.batman-online.com/forum/proxy.php?request=http%3A%2F%2Fmondesign.net%2Fkremzeek%2Fcompare1.jpg&hash=ca680b108544e80b4d2065f96ad31272d2bc4f68)
And here is the museum's interior design in one of those collectors' cards.
(https://www.batman-online.com/forum/proxy.php?request=http%3A%2F%2Fwww.tradingcarddb.com%2FImages%2FCards%2FNon-Sport%2F74646%2F74646-165Fr.jpg&hash=dfb709247539e133e4582daac8731ed1d54ce1bf)
I don't really see the fascist influence in B89. Crime noir, deco, industrial, those influences are clearer but the stripped classicism/fascistic design elements aren't really clear to me.
Thanks for the images, thecolorsblend.
True, Batman Returns had more of the german expressionism / fascism.