Cognitive science emphasizes the strength of visual formalisms for human learning and problem solving. In software engineering, a clear, visual presentation of a system's architecture can significantly reduce the effort of comprehension. Yet, all too often the documentation of complex software systems lacks clear identification of the architectural constituents and insufficiently relates them to the source code. It is our contention that visualization of the architectural constituents within the source code model is an indispensable aid for the guided evolution of large-scale software systems. We present a prototype tool for visualizing both published, generic design patterns as well as well-thought, ad-hoc design solutions, given the reverse-engineered source code of a system. We discuss the architecture and core functionality of this tool, addressing source code reverse engineering, design repository, design representation, and design clustering. Then, we present our visualization objectives and detail our techniques for pattern visualization. A case study example helps explicate and illustrate our work.