For many years now scholars have been developing an App which would allow us to see Rome as it was around the year 320AD at the height of its architectural wonder.
It is also the year the Emperor Constantine decided to leave Rome to create a new Capital Constantinople (Istanbul). The view of Rome is not that of the era of Julius Caesar or Augustus or Nero but much later. Nonetheless it is how Rome of Antiquity is remembered today. It is very helpful because if you visit Rome making sense of all the ruins can be very difficult and bewildering. Most people concentrate on the Colosseum because it is the easiest to understand and just forget the rest. Even scholars have a tough time of it, unless you have studied the periods from the birth of the City to its decline 1000 years later, too many details and too many people to remember. I have a dictionary at home of Whose Who in Rome to make sense of it all.