Aim. This study is an ethnomathematical study that aims to describe and interpret the philosophical value and geometrical patterns of the famous architecture and ornament of the Indonesian traditional Mosque. Methods. This report subsequently used an ethnographic method, with data being obtained through observation, documentation, and Focus Group Discussion (FGD). Furthermore, the study subjects were a cultural practitioner and a group of educators, containing five primary school teachers in Central Java, Indonesia. Interviews, observation, and documentation were conducted during the research. The data was analysed qualitatively. Results. First, from the data analysis, it was found that there are several philosophical values contained in the architecture and ornaments of a Javanese traditional mosque such as the relationship that must always exist between humans and God and fellow human beings, Islam, iman (faith), Ihsan (kindness), openness, honesty, obedience, and humility. The second indicates the relationship between the Javanese architecture and ornament of the Indonesian traditional Mosque and the geometrical patterns (the cuboid, and cylinder), symmetrical patterns, and geometry transformation (rotation) used as the source of learning and starting point to the mathematical learning process. Conclusions. These results were specifically useful to primary school teachers when teaching geometry. Through culture as a context or starting point, the new mathematical learning resource was also used for geometric learning. In addition, the philosophical significance of these artifacts fostered an interest in the indigenous culture and good character values.