Cyclorama
The largest single piece of scenery in the theatre is the cyclorama or "cyc". As the name implies, it encircles or partially encloses the scene to form the background. It's most familiar use is as a sky or void backing a setting or elements of scenery placed in the foreground. Occasionally it is painted with a decorative or pictorial scene to fit a specific show. Interestingly the cyclorama can be manufactured as a rigid cyc (hard scenery) or flexible cyc (fabric). The majority of theatres tend to favor the flexible cyc as it permits being moved more easily.