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. 
Did politics stand in the way of the construction of which building in the Eternal City?
Cocytus