Since you landed on the ArcGIS Urban GeoNet space, it seems very likely that you've already heard about ArcGIS Urban. Have you also already heard about CityEngine?
If yes, then check out this blog post written by my colleague Taisha Fabricius about how CityEngine and ArcGIS Urban play together.
If no, then it might be interesting to know first that CityEngine is an advanced 3D modeling software for designing urban environments. With this in mind you are now also ready to read the blog post mentioned above.