Here’s a large photo set posted on Flickr, by a user called MrJennings, showing Italo Gismondi’s Model of Imperial Rome, at the Museo della Civiltà Romana. The 1:250 scale model depicts the city in the time of Constantine. Snapshots of the model turn up frequently in the context of articles about the imperial city, but this is a rare look at the work itself in its entirety. Meanwhile, here’s a more interactive look (zoom, pan, etc.) that also includes a bit of a description.