Through the magic of Google Earth you can now travel back in time to see Ancient Rome and all of its architecture in full 3D. The feature was developed by the Rome Reborn Project which aims to recreate a 3D representation of the ancient city of Rome from the year 320 AD, at the peak of the city's development. To rediscover the 3D city of Ancient Rome for yourself, check out Google's page about the new feature.
Of course, that's assuming you can get the feature to work. When I and a colleague tried to take advantage of the new feature, it did not appear to be fully implemented yet. The Ancient Rome 3D map is supposed to appear as a Gallery Layer in Google Earth, however after downloading and installing the latest Google Earth updates multiple times the layer never appeared available for either of us. Hopefully Google will get whatever issues it is having ironed out soon, because from the preview video on Google's page it looks to be a very impressive feature. But I guess it's true what they say, "Rome wasn't built in a day."