I've tried different settings of clamping, sun/no sun, lamps, emission, higher samples, etc... but I can't seem to get rid of them. Not keen on blur nodes or similar since I need to see the inside of the apartments > people, furniture, etc... And I also need reflections from the windows so I don't want a hole instead of windows.
Download Blend file here: http://we.tl/2oPC7y4zdc
And please don't mark this as a duplicate cus I've tried finding answers here on blender.exchange, Blender Guru and YT without any luck as you can see.
Note: I'm a total noob. Just started Blender about a month ago.