Reflection and translation material are critical to be mastered by students in learning transformation material. However, reflection and translation material are still difficult for students to understand. Therefore, this study aims to develop a learning trajectory that will assist ninth-grade students of Junior High School in grasping the notion of reflection and translation in the context of the Sam Poo Kong Temple in Semarang. The research used the design research method, which consisted of three stages: the preliminary design, the design experiment (pilot experiment and teaching experiment), and retrospective analysis. The PMRI approach was used to develop learning activities in this research. This study involved 32 ninth-grade students at a junior high school in Semarang city. The results of this study is a learning trajectory that includes a series of learning processes in four activities. These are observing the Sam Poo Kong Semarang video and analyzing the properties of reflection, finding the reflection formula, analyzing the properties of translation, discovering the translation formula, and solving contextual problems related to reflection and translation. The activities conducted can enable students to develop a better understanding of material reflection and translation. The research's findings indicate that using the Sam Poo Kong Semarang temple context can equip ninth-grade students to comprehend the concept of material reflection and translation. Additionally, the outcome of this study offers additional local wisdom options that can be used as a context in mathematics.

Sam Poo Kong is one of Semarang's city cultural heritages. This historical structure features intriguing architecture as well as being a popular tourist destination.  This study aims to explore Sam Poo Kong's building as a starting point in the geometric transformation course. Besides, the study method is descriptive in qualitative terms with the ethnography approach, namely the type of research to describe and acquire data as a whole, comprehensive, and in-depth. The result is an ethnomathematics exploration of Sam Poo Kong's historic buildings, representing mathematical concepts including reflection, translation, rotation, dilation, and cultural values. Based on implementation in transformation class, students can quickly grasp which Sam Poo Kong's building portrays transformation.Students can identify and describe the Sam Poo Kong building's transformation forms, which include: 1) reflection on the temple as a whole, ornaments, and Sam Poo Kong entrance gates; 2) translation on the statues, roofs, lanterns, and poles; 3) rotation on the bedug, reliefs, incense holders, lanterns, and anchors; and 4) dilatation of the inner and outer rooflines of the Sam Poo Kong building. This can stimulate students to envisage the types of transformation, which makes the information easier to learn.Moreover, this study can benefit teachers for local wisdom context reference in geometric transformation and following researchers for further study.