Can anyone recommend code dependency tool?

I've just started a new job and I find myself in the familiar position of having to become proficient with a large codebase that only has basic auto-generated XML files as documentation.

Could anyone recommend a good Windows tool for getting an overview of a class hierarchy within a solution/project? What would be particularly cool would be a tool that would also show in its overview whether a given class could be multiply instanced or is a Singleton, but any tool's better than nothing.

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Mijin