Redesigning city

Hi, I’m redesign my city. I have a lot of screenshots of things I like but was wondering what’s your take on the location of factory/production buildings. I see a lot of them hidden away in a corner, but also a lot in the convinient place close to GTHQ etc. I don’t mind spending some simoleans to get nano tech factories. Looking for any tips on this matter, but also for general redesign. Thanks in advance