I'm sure this is a FAQ, but I can't find an answer which works.  I have a document in portrait mode (A4), with one wide diagram - a Gantt chart, created with the gantt-tikz module, and which I'd like on a landscape page of its own.

What's the easiest way to do this?  I can do it by simply putting the chart on a page of its own and rotating it, but this is a bit of an ad-hoc solution.

Thanks,
Alasdair