This textbook develops geometry for students in primary education based on five key concepts: Geometry helps us perceive spatial relationships and orient ourselves in space; it aids in understanding shapes and (artistic) designing of patterns. Additionally, it deals with measuring objects, especially inaccessible ones through theoretical tools, and helps us represent our reality using maps and plans, as well as design realities in a planning context. The necessary mathematical background knowledge for geometry teaching in elementary and early secondary education is practically and theoretically elaborated upon through these key concepts. The readers are encouraged to make their own discoveries. Therefore, the experience and exploration of P. are emphasized.