The Invisible Art

This book is all about the art of matte painting - there are countless images of before, after and in-between shots of scenes of movies that have used matte paintings. 
There are a couple of images of Darby O'Gill & I've also included the scenes the matte paintings were done for. The mattes match seamlessly. In the videos you'll also spot some other special effect techniques such as the King Brian puppet and bigatures.

The set of the castle ruins atop the Knocknasheega mountain were built large enough that Darby could walk through without walking through the matte paining.
The image of the ruins atop the hill in the beginning of the clip is also a matte painting.

 

This scene has a lot of special effects going on, not only the matte painting but there is forced perspective - the scene of Darby walking into the cave was set up so that the camera was looking through the matte painting and through a a mirror. Again there are more puppets and some bigatures for the leprechauns.

Here we have a nice in-between image of the scene; to save time, space and money, only a partial set was made (upper left) and everything that is blacked out (lower left) is replaced by the matte painting. Again we see another King Brian puppet, as well as one for the cat.