I'm working on a story about another dimension of this same Earth but without the same human development and history. The land and natural conditions would be the same except for the ones directly affected/created by humans.
In this dimension, I want a human society living IN tree cities (cities created inside giant trees). I've already though of the "technology" possible for that and how a few selected trees became giantic (short version: humans are really good at bioengineering in this dimension). The trees would be from different species autoctone to each the zone (Iberian peninsula, in this case).
However, I'm not sure how big those trees could be but I'm sure there are physic limitations for that.
I don't want a massive city yet I would like if it the tree could be big enough to contain a minimun of a thousand people but, hey, the more the merrier!
So, basically, How big (height and witdth)could a tree be keeping the Earth physical laws?
If you need more info or details, here I am!
edit: the tree extra-needs (such as more nutrients to keep growing or those nutrients reaching the parts of the trees needed) are handled by the humans living in it.
edit: To be more specific as it seems that the question is not clear enough. I don't know much about physics but I though maybe the athmosphere or the weitght of the branches/leafs could affect its size.