This research aims at studying on how students develop their spatial visualisation abilities. In this paper, one of five activities in an ongoing classroom activity is discussed. This paper documents students' learning activity in exploring the building blocks. The goal of teaching experiment is to support the development of students' spatial visualisation ability and to study about how students visualise and interpret the building blocks. The analysis of the activity is focused on exploring how the building blocks activity develop students' spatial visualisation, various way of students' interpretation and visualisation of building blocks, and how teacher affect the way students visualise and interpret the building blocks. The results of this study show that the building blocks activity supports the development of students' spatial visualisation ability.