Abstract: A skylight system including a light-admitting cap adapted to fit over a grooved flashing is disclosed. The grooves are constructed in such a way that they will dissipate heat and remove condensation, but they will not admit the passage of unwanted objects, such as dust or bugs, and they are placed in the flashing rather than the cap so as to allow the cap's form to be less obtrusive than would otherwise be possible. The flashing is formed of a single piece of material, which may be aluminum, to reduce the likelihood of warping, or of cracks forming therein. The system further includes an extension tube communicating between the structure's exterior and a desired location inside the structure, and an inner trim ring with a filter and a diffuser adapted to moderate the intensity of the admitted light.