This is the Tower of the Beholder Mage. the basement is for alchemical research. The ground level is for greeting visitors, guards quarters and research of beholders. The middle levels are for research, lodging of visitors and acolytes. The center of the tower houses the Acaxian Crystal for teleporting the tower. The top levels is the Beholder Mages quarters.

As to play design for D&D, this is a vertical mage tower with a Beholder Mage. One wish goes wrong, and now there is an actual Beholder in the tower with quite the drop. The party had better bought ranged and feather fall because its going to be a rough ride to the end.