You can’t find it because it doesn’t exist. There is no page at that location.
In WordPress everything is either an archive of posts or a post of some type. Pages are posts of type page etc. Date archives are archives of posts
So if you went to /category what would it show? For this reason there is nothing there to show. You would need to write a rewrite rule, manually load a template, and that’s assuming it doesn’t interfere with other rewrite rules