Glass Wall

This is the clean way to get daylight into a build without opening a hole in it. Player-placed walls stop enemies appearing behind them and these count, so a whole facade of glass is as safe as one of stone while you can still see out. Sunlight passes through, which means a surface room walled in glass needs far fewer torches than the same room in brick.

Two things to expect. The pattern on a placed section can shuffle itself when you reload the world, so do not build a design that depends on which pane sits where. And the stained versions are made out of these plus gems, which sell for roughly what the gem was worth, so that route is a conversion rather than a profit.