Hi , i have a problem

I need to make an industrial park in maya , the problem here is that it is so big , and i really don´t know at what size i should start modeling it .

I use like reference the grid that maya shows, but i dont know if it´s good enogh .

because some of the buildings have a to much detail.



i´m going to attatch the image that i´m using as base, and another image of how the buildings should look.

i hope that someone can help me or giveme advice of how should i start my modeling