This study describes how a group of grade 7 and 8 students in South Africa engaged with the notion of spatial scale in the Universe before, during and after a visit to an astronomy science centre. A limited amount of research has been conducted on this concept worldwide. Using a combination of concept maps, observations and interviews, results indicate that, despite contrary suggestions in the literature, students aged 13- to 15-years are able to improve their conceptions of size and distance from naïve and conflicting knowledge to a more scientific understanding after their visit. The findings also demonstrate, using a human constructivist framework, that students showed both weak and strong restructuring of knowledge. Experiences with size and distance also appeared to be important in the students' affective domain. The paper argues that a combination of related, themed experiences related to spatial scale can account for the improvement, and recommends that these and even more innovative activities should be explicitly promoted at science centres and in out-of-classroom activities.