That is the Project Origin, it is the 0, 0, 0 point of the project. It can be moved but not disabled. If you want it at the center of your project, then move all the elements rather than the Project Origin. You can read more about it in the help files.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your Archicad version and operating system (see mine for an example) for more accurate help in this forum.