These are architectural features that allow natural light from outside to illuminate interior spaces. If "solid paper" is a misunderstanding or miscommunication, and you're actually referring to a material that lets light in (like glass), skylights or clerestory windows could be what you're interested in. They can be used to bring light into upper floors.
Then there are the , mysterious individuals who seem to possess the ability to communicate with the portraits in the Whispering Gallery. They move unseen, their whispers weaving a subtle spell that draws the curious deeper into the labyrinthine corridors of Yhivi. the upper floor yhivi