To commemorate the birth of Augustus (63 BC) two thousand years earlier, Mussolini commissioned a model of Rome as it appeared at the time of Constantine (AD 306–337), when the city had reached its greatest size. Constructed by Italo Gismondi from 1933–1937, later extended, and restored in 1990–1991, the model is built to 1:240 scale (as is the marble map of Severus) and extends more than fifty-five feet across. It and other materials from the 1937 exhibition are displayed in the Museo della Civiltà Romana (The Museum of Roman Civilization).
The model is based on another exceptional work, the Forma Urbis Romae by Rodolfo Lanciani (1893-1901).
