This is a small example on how to use assets in Unity in ways they are not always intended, nothing crazy and you would get much better result by doing a custom asset entirely but you can still get descent results!
Asset Store
The assets used here come from an interior pack which you can get here : https://www.assetstore.unity3d.com/en/#!/content/18139
This is a very good asset pack and well worth the price 🙂
Be Creative!
For the watch tower i just use a few of the walls and wood supports. Don’t hesitate to experiment, you can stretch stuff a bit as long as it doesn’t become super obvious that it’s been deformed. Research pictures on what objects / building you want to do and try to rebuild it with whatever you have 🙂
