I would use the tips and information included in previous discussed threads that will help you create realistic terrain features. I’m no terrain builder but gathering experience from other developers will inspire you. View resources and tutorials, as that’s the only way you will learn.
There are countless of terrain plugin that can create realistic approaches with using them and just using the common basic tools ‘terrain editor’, always experiment with it to get comfortable and testing different methods. Using plugins aren’t needed for creating realistic terrain but it will come in handy for adding realism elements start small and you will eventually improve. Refer: