User blog comment:IamJakuhoRaikoben/Chapter 456: Order, Review./@comment-24102956-20151013095648/@comment-7418318-20151013180000

There was nothing like that because the building was built on top of the ground.

Shrinking the entire city would mean also shrinking the soil, unless you mean to say she should shrink every single building by itslef, which is something different. But even then it might still be problematic if she was to shrink a building with a cellar.