This study is mainly concerned with legibility in urban environment in an attempt to find the kind of the relationship between changing the structural propertires for the space discipline in legibility of the mind picture for the witness and indicating the significant.Lastly, planning for historical cities in Iraq is aimlessly done and it lacks the scientific fundamentals.The problem of the study is that there is no cognitive vision which clarifies the relation between changing the structural properties for the space discipline in legibility in urban environment receiver according to the hypotheses of the research and to achieve its aim, the researcher was adopted two scientific ways: the first one the structural method- through using of arithmetical way in indicating numerical weighs for space structure .The weighs express the relative for the structural parts. The second one: the perceptional method: by using questionnaire to know the mind picture for the receiver which results from the difference of the legibility degree in urban environment and indicating the place of indicator points in the city. For the purpose of the research and to achieve and treat the research problem in accordance with the aims of the research , the researcher, chose AL-Kefil City as a historical city as a sample of the study for its importance from the historical point of view to reach up some conclusions and recommendations.