The path bar (the buttons, not text) in Nemo usually shows the path relative to a "well-known" location, e.g. /home, or /media. There's a tiny button you can click to expand this to show the whole rooted path. But once expanded, I can't see any way to collapse it again - is it possible, or did no-one think of it?
It always starts collapsed in a new window, but it seems that if you expand it, that's how it stays in that window. Even switching to the location bar and back doesn't change it.
It's a detail, but I just don't like actions that don't have an opposite!