The ArcGIS Maps SDK for Unity includes a comprehensive C# API that allows you to set up custom scenes. Browse the table of contents to the left of this page to explore the classes and components that are available.
The SDK samples include scripts that use the C# API, which can be found in:
Assets/Samples/ArcGIS Maps SDK for Unity/1.0.0/All Samples/Scripts
If you do not have the sample folder, be sure to import the sample assets.