Do not look for the Danteum in the Eternal City. In true Dantean form, politics stood in the way of its construction in 1938. Ironically this literature-inspired building can itself most easily be found in book form. Reading this book I remembered Goethe's quote about frozen music. Did Terragni try to freeze Dante's medieval miracle of song? Certainly a cold-poem seems artistically repulsive. Unflattering comparisons to the lake of Cocytus spring to mind too. While I cannot read Italian, I can read some German. After locating the original quotation I discovered that 'frozen' is a problematic (though common) translation of Goethe's original 'erstarrte.' The verb 'erstarren' more properly means 'to solidify' or 'to stiffen.' This suggests a chemical reaction in which the art does not necessarily chill in the transformation. Nor can simple thawing yield the original work. Like a chemical reaction it requires an artistic catalyst, a muse. Indeed the Danteum is not a physical translation of the Poem. Terragni thought it inappropriate to translate the Comedy literally into a non-literary work. The Danteum would not be a stage set, rather Terragni generated his design from the Comedy's structure, not its finishes. 
Who created the Danteum?
Terragni