You'd be surprised what people have created in the base editor! Someone posted pics of a tank while another posted pictures of the Millenium Falcon. All you need is a little Dew and alot of time.
You forgot the desire to torture yourself. 
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I have tried concave domes ceilings before. I think you are gonna have to give up the same texture, but what I try to do when I cant find a solution is to make some sort of conflict in the continuity, if that makes any sens. Example, If you cant make a dome, then make damged whole in the ceiling.. as if the dome had collapsed... and make the ceiling look like the sky? Or build it damaged and build a scaffold to make like its being rennovated.
I made a Millenium Falcon in my base, one that had walk through to both upper and lower turrets and hidden stroage space. The problematic concern during the whole build was how the heck am I supposed to make the cockpit... I tried flourescent lighting to spoke it... that didnt work, I tried item of power.. that only worked to a certain extent. I even tried control desk's profiles for the lower half of it.. that didnt work.. so with all that crap that didnt work ,floating there, I decided to put the control item to look like a kind of hangar's repair station, and IMO it was thee only solution, because the hall to cockpit wouldnt travel through anyways.
City hall OMG it just occurred to me you might have meant the outside. LOL nevermind. But if you meant the inside. the first paragraph applies. God, at this point why did I even post this.
I hope I helped in some way.
Idly looking at a loading screen and I wondered if it's possible/has anyone built an Atlas-like City Hall in their base?
Textures will be tricky but there's that half dome for the top and there's pillars in the editor.
Any pics/further ideas before I lose what little sanity i have?
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