Lightwell

In architecture, a lightwell, sky-well, or air shaft is an unroofed or roofed external space provided within the volume of a large building to allow light and air to reach what would otherwise be a dark or unventilated area. Lightwells may be lined with glazed bricks to increase the reflection of sunlight within the space. Lightwells may have sunlight reflecting mirrors on the top of light well.

Lightwells serve to reduce the necessity for electric lighting, add a central space within the building, and provide an internal open space for windows to give an illusion of having a view outside.