In this study, a STEM activity was designed and implemented for eighth-grade students. The activity was used with thirty students and involved the construction of various hologram pyramids. During the activity, the mathematical concepts used in designing the hologram pyramids were discussed and the resulting hologram images were compared considering reflection laws and characteristics of an image formed by a plane mirror. Moreover, the angle of the pyramid's surface in relation to the horizontal plane was discussed for the purpose of obtaining a clearer hologram image. It was revealed that the activity designed by the researchers is relevant for improving students' knowledge and skills related to STEM. Furthermore, the fact that the hologram pyramid was created by paper folding, as opposed to using the design methods reported in the literature, made the activity suitable for middle school students. Finally, suggestions for teachers who wish to implement the activity are offered.