Before CGI, They Used Mirrors

If you haven't stumbled upon it already, take a moment to read through this explanation of the Schufftan process, a movie special effect that relies on angled mirrors, miniatures and clever lighting to superimpose actors into environments that did not exist. It's green screen before green screen.

There are plenty of videos out there demonstrating the effect but the GIF above is the perfect mindblowing introduction to the concept.