] Oh dear. This is one situation where the stuff that exists on-line is extremely misleading indeed, I'm afraid.

The link I posted here does have information consistent to what you are saying here, though.

]The Grecian temple has as special symbolic significance in 18th century gardening, that has to do with lasting goodness and universality. I think Marianne wandering in a Grecian temple is a sign that she thinks of herself as heroically tragic.

The point I wanted to make though is that Marianne earlier in the story has been a vocal proponent of the picturesque and Grecian temples were not part of that style, from what I read--rather the opposite, as the picturesque landscape or garden would have ruins rather than a temple.

However, I can totally buy that Marianne would find great appeal in thinking of herself as heroically tragic :-)