Ask HN: Diagramming Tools for Explaining Codebases

[throwawayswe]

I inherited a medium-to-large sized, high-complexity C++ codebase with outdated documentation. The documentation was written when the project was in the design phase and the implementation differs in several ways, large and small. I want to document it for myself and those coming after me, and am missing a tool that will help me generate diagrams quickly for a high-level picture. I am familiar with Doxygen and Graphviz and will be using those. The code is heavy on C++ templates, so bonus points if it "gets" templating.