The purpose of the study is to identify the classroom mathematical practices developed within a learning environment designed by Realistic Mathematics Education for teaching cone and pyramid to preservice teachers. A teaching experiment including five-week instructional sequence by a hypothetical learning trajectory about the solids of cone and pyramid was conducted to five preservice middle school mathematics teachers. Their learning was examined in this teaching experiment performed based on case study as a qualitative research design. The social learning environment in the classroom was investigated by three-phase methodology of Rasmussen and Stephan (2008) developed based on Toulmin's model of argumentation. According to the findings, four mathematical practices emerged in the current study.