The classic in-camera effect to trick the audience’s eye.
Director Michel Gondry demonstrates a forced perspective set from his film Eternal Sunshine of the Spotless Mind (2004):
For scenes with humans and hobbits, director Peter Jackson employed more advanced, moving camera techniques in his The Lord of the Rings movies (via TXFilmProfessor):
Filmmaker IQ offers a deeper dive into the math which makes forced perspective work:
Try It Yourself
DIY film-maker Steve Ramsden shows how to convincingly make a model car look life-sized in your shot…
… and offers more extensive tips on working with miniatures: