He wanted to show the world how brilliant fascism was (I am cynical), so he organized a World Expo meant to open in 1942, the "Esposizione Universale di Roma".
A whole new borough, just outside the city center, with wide lanes and impressive neoclassical buildings.
Quite a megalomatic enterprise, and this building was meant to be the highlight: the Palazzo della Civiltà del Lavoro. (the palace for the civilization of work).
It's also sometimes referred to as "the square colosseum".
Anyway, a worldwar interfered, and the area was never totally finished. What is left is a city layout and some stark buildings, whose architecture is not even all that bad. It's meant to impress, and it does that very well.
I just get a foul taste in my mouth recalling where these ideas originated.