In this paper we introduce PRIMA: A PRecise vIsual language for Modeling with Agents, in a physical environment. Our objective is to design an expressive Domain Specific Visual Language for building agent-based models. Models in PRIMA are diagrams, which describe the agent structure (i.e. actuators and sensors), behavior, instances and environment topology. We show the use of metamodeling techniques to describe the multi-view language PRIMA, its definition in the AToM3 tool, and the generation of a customized modeling environment for it. Keywords Domain Specific Visual Languages, Metamodeling, Agent-Based Simulation, AToM3 .