The goal in this article is to support teachers in better understanding what it means to model with mathematics by focusing on three key decision-making processes: Simplification, Relationship Mapping, and Situation Analysis. The authors use the Theme Park task to help teachers develop a vision of how students engage in these three decision-making processes in an elementary school classroom. Following this discussion, the authors reflect on the implementation of this task, giving attention to the roles that student autonomy and task selection play in the use of modeling with mathematics. Using simplification, relationship mapping, and situation analysis as a framework, the authors offer vignettes of student discussions about the Theme Park task to highlight their key choices as they model with mathematics.