Minimum radius = 2nd radius

 

This fictional plan has lots of operating potential, and includes some classic locations from children's railway stories. The turntable can be used to depict any number of stories, including my childhood favourite of when a pompous loco falls into a ditch. A quayside could be built into the lower right hand corner, with the mainline passing close by. The branch line allows for a tank engine to run round two small coaches.