The Big Agile board is used by upper management to track the execution of their vision. Making it visible increases the level of transparency, which is probably the most crucial aspect of this. At the very least, make sure there are no surprises along the lines of: "How's that very important thing I asked you to work on coming along?" and "Erm, yes, been meaning to tell you about that."

How we set the board up will differ from context to context. It may be that you have your teams and the executive team in one location, in which case this could be as simple as making each of the roadmaps visible: a war room style wall, which incorporates updates from the teams as they progress.

The key to any Agile/Lean endeavor is to expose the system to itself so that people within the system can identify problem areas and make continuous improvements. Without first making the problems visible—especially if we keep seeing information piecemeal—it's impossible to actually spot what is happening and how to unpick it.