Generally Cupolas are used as a decorative accent to roofs. Our Square, Octagon and Dodecagon gazebos have open, functional cupolas in part because it allows for an easier installation. Ventilation can be a concern if the gazebo is enclosed with privacy panels or 4 track windows. You can add a functional cupola to any of the gazebos by selecting this option. A cupola box will be incorporated into the frame of the roof, so there is nothing more to do when building your gazebo.