preserveAspectRatio / viewBox

Hello,

I am struggling to understand the concepts of coordinate transformations and
nested objects.  What I would like to do is create a viewbox that has an
aspect ratio that is different to the svg width and height but I don't want
to preserve the aspect ratio.  Inside that viewbox I would like to create
another element but preserve it aspect ratio.

I'm hoping someone can suggest a best practice for this.

Thanks