It's impossible for anyone to see what ancient Rome looked like in all of its splendor, since we've failed to invent a time machine. But the above video, which shows a 3D rendering of Rome in 320 AD, is about as close as we can get.

The video was created by Rome Reborn, an academic research project whose central mission is to create a full model of Rome at its greatest heights, working in conjunction with the Khan Academy and Smarthistory. The goal is to take historical depictions of the city and create a true-to-life model of every period of Roman development, ranging from 1000 BC to 552 AD. This isn't just a cool pastime; it's useful for everyone from historians to filmmakers looking to capture what the city actually looked like.

In the video, Indiana University professor Bernard Frischer (who leads the Rome Reborn project) explains that they chose to use 320 AD for this visualization because it was "the peak of Rome's urban development." Ten years later, the emperor, Constantine, moved the capital to Constantinople (present-day Istanbul), and the city of Rome began to decline. (The Roman Empire itself went on to survive, in various forms, until roughly 476.)

The most striking part of the video is the sheer scope and beauty of the city.

But there are a few interesting factual tidbits, that stuck out from the video, too:

At this point, Rome had somewhere between 1 million and 2 million residents. For perspective, 2 million residents would make Rome bigger than every American city today except for New York, LA, Chicago, and Houston. And this was 1700 years ago!

Interestingly, Rome itself isn't built near potable water. According to Frischer, the Romans managed to support a modern-size metropolis using an absolutely massive system of aqueducts — literally "roads for water" that brought in clean stuff from nearby mountains and rivers. The video gives you a great sense of just how huge those aqueducts had to be.

The video shows the Colosseum as it would have looked at its full size, which is truly colossal. We also learn that the Colosseum wasn't what Romans called it (that name dates to later, in the Middle Ages). It was actually called the Flavian Amphitheater, built by the Emperor Vespasian in a bid to gain popularity after his mad predecessor, Nero, allowed huge portions of the city to burn down.

There's lots of other interesting stuff, including a fascinating discussion of how the Romans thought about architecture and beauty.

Be sure to watch the whole thing, and thanks to Realm of History's Dattatreya Mandal for flagging it.

Video: 220 years of population shifts