Is it a haunted house? A black cave? A hole in the universe? Or is it Louise Nevelson’s “Sky Cathedral” as described by a kid? MoMA’s new animated series “Once Upon an Artwork” is for the kids in your life—and the kid in you. To create each episode of the series, we recorded audio of children looking at works of art in MoMA’s collection. Using the audio, an animator then brings each child’s unique vision to life. In this episode, Nova peers inside Louise “Sky Cathedral” and finds a haunted house