clerestory

noun (plural clerestories)

• the upper part of the nave, choir, and transepts of a large church, containing a series of windows. It is clear of the roofs of the aisles and admits light to the central parts of the building.
• the windows in the clerestory of a church or similar windows in another building.
• a raised section of roof running down the center of a railroad car, with small windows or ventilators.