As many have probably already told you, it's in the Pisan Cantos.

Tom White wrote:


>Can anyone help me on this? A line in French sticks in my head that  
>goes like this:
>
>Le Paradis n'est pas artificiel.
>
>I thought it might be Pound but can't find it using Terrell's Index  
>and that idlest of all approaches, paging through the Cantos.
>
>I know Pound said, "I have tried to write Paradise" in Canto CXX,  
>emphasis apparently on the "tried," but that's as close as I can get,  
>along with, "To build the city of Dioce, whose terraces are the color  
>of stars." Dioce as a kind of paradisal place mentioned several times  
>elsewhere.
>
>Thanks, Tom White, Odessa, Texas.
>