Adding natural light from ceiling/shaft?

[guigr]

I noticed that there are beautiful natural lights in some level mostly coming from shaft, cave in but I can't find any reference to it in the help.
Anyone can explain to me how it works? I want to improve the atmosphere of my dungeon

[Lmaoboat]

prison_ceiling_lamp
temple_ceiling_lamp

[guigr]

Thanks a lot! I was working on dungeon levels so i didn't notice that.