Saw a documentary called Mussolini, Monuments and Modernism and a couple of things caught my eye.
Celtic Tumuli, Ireland (LV-223 facility)
Necropolis of Pantalitica, Sicily (mountains sides around Engineer City)
Memorial Of Redipuglia (the square and stairs in front of the Engineer citadel)
Stadio dei Marmi, Foro Mussolini (I imagine the arena/colloseum from an earlier draft looking something like this)
While searching for images I saw this. We already compared Engineer City to Vatican City. Like the square, with the circle in the middle.
But now I noticed the pillar walls to the left and right of the circle are also similar. Just like the gate in the back of the square.
And the point of view is similar to David's on the balcony.