This article is aimed to consider the property of geographic maps which is not very well studied but is always used by specialists (as well as by nonspecialists) that is to disclose new features of the objects drawn on maps which is not possible to disclose using non-cartographic methods. The sources of this property are complete and exact reflection of phenomena on the maps and consequently the use systematic methodological approach. The point of maps as cognitive systems is justified. The content of the property under consideration is established the objective cognoscibility of maps.