The set and the special effects were led by a clever series of screens and overlays with figures and lighting to make them 3-dimensional. And the buildings and other two-dimensional objects were built on angles to force the horizon and perspective on the audience.
I'm not saying it was perfect. There were microphone problems with the first few scenes, including the Wicked Witch of the West's grand entrance. And the whole thing got louder and louder and louder until I grabbed my earplugs after intermission. With so many children in the audience, the applause was not terribly contagious, and a few scenes didn't get the recognition they should have received.
My hands-down favorite part was the scene where the winged monkeys flew to go capture Dorothy - the music was "Night on Bald Mountain."