Insight in the global structure of a state space is of great help in the analysis of the underlying process. We present a tool to visualize the structure of very large state spaces. It uses a clustering method to obtain a simplified representation, which is used as a backbone for the display of the entire state space. With this tool we are able to answer questions about the global structure of a state space that cannot easily be answered by conventional methods. We show this by presenting a number of visualizations of real-world protocols