A cupola is a small, often dome-like structure on top of a roof. They are used for both decoration and ventilation, and can be found on all kinds of buildings from churches to barns. While some people believe that a cupola needs to be centered in order to look best, this is not always the case. In fact, many architects feel that an offset cupola can add interest and visual appeal to a building. So, whether or not you center your cupola is ultimately up to you and what you think will look best for your particular structure.