Our students built a full-size, mobile planetarium in three weeks. The planetarium was built with commonly available, cheap construction materials. Our priorities were mobility, possibility of quick assembly and reassembly and the students' availability of materials in every place in the world. The students calculated all the parameters of the planetarium's construction themselves, chose materials of appropriate technical parameters, built the planetarium's framework, elaborated the methods of projections and sounding. Taking into consideration the spectators' comfort they also designed systems of air conditioning and cooling. The project is completely consistent with the STEM and even the STEAM method. The artistic factor of the students' work was revealed during the visualisation of planetarium projections and its adornment. The final product of their work is a functional planetarium and a manual for its construction.