lightwell

From light +‎ well.

lightwell (plural lightwells)

1. (architecture) An open shaft that transmits light from above into a staircase or an inner room.

   Synonyms: airshaft, air well, ventilation shaft, vent shaft

   • 1907, Ronald M. Burrows, The Discoveries In Crete, page 80:

     In it a covered porch and vestibule were backed by a vertical shaft or "light-well," which served as a great window both to the vestibule itself, and to the corridors, staircases, and landings that connected it with the upper stories.

   • 2017, Kamila Shamsie, Home Fire, Bloomsbury (2018), page 240:

     The sliding glass door with its rolled-up blinds looked onto a lightwell, composed of a glass platform overhead and carefully angled mirrors that were reflecting a confusing cold light into the bedroom.

• lightwell on Wikipedia.Wikipedia