Player Core
Chapter 8: Playing The Game
Movement
Tactical Movement
Moving Through a Creature's Space
Objects
Source Player Core pg. 414
Because objects aren't as mobile as creatures are, they're more likely to fill a space. This means you can't always move through their spaces like you might move through a space occupied by a creature. You might be able to occupy the same square as a statue of your size, but not a wide column. The GM determines whether you can move into an object's square normally, whether special rules apply, or if you're unable to move into the square at all.