My favorite Matte work in a film is by far from "Ghostbusters"
This Youtube clip kind of sucks to see the Matte work, but here it is
But they created a 360 degree Matte of New York City all around the stage, the skyline looks real, with blinking lights, amazing looking buildings, as well as the changing sky, and the top of the building that they are on
I am not using "Ghostbusters" as proof of alteration, just stating that I love the Matte work