Can You Build It? is an engaging Improve It! task that asks children to construct 3D shapes based on 2D depictions. Students' initial 3D creations often need revision, and as they build and re-build, they develop spatial relationships. This task was implemented in a first-grade class, connected to composing 3D geometric shapes to address the Common Core State Standard 1.GA.2 (National Governors Association Center for Best Practices & Council of Chief State School Officers, 2010). Moving constantly between 2D and 3D leads to a stronger spatial sense that helps students to unveil the shapes' structures, which is an important topic in mathematics and recommended as a mathematical practice. This article examines how first graders' abilities to build and improve their geometry constructions while moving between and connecting 2D and 3D representations. Because the task is primarily about students constructing and exploring, the lesson was organized into three stages: (1) presenting the task to students (10 minutes); (2) students constructing and improving constructions, alone or in peer groups (30--45 minutes); and (3) a whole-class conversation with students presenting and discussing strategies (15 minutes).