The antonyms for the word "un-built" are numerous and include "constructed," "built," "assembled," "erected," "established," "erected," "raised," "completed," "finished," and "developed." These words represent the opposite meaning of the term and indicate that a structure, building, or project has been completed or realized. In contrast, "un-built" refers to something which has not been built or realized yet. When it comes to planning and designing, antonyms for "un-built" would include "designed," "drafted," "mapped," "planned," and "blueprinted." These words show that the structure or project is in the planning stages, but not yet realized.