The final window in the A to Z. I posted about Zadar quite recently so no link for this picture.
The rose window developed out of the oculus, a small round window found in Ancient Roman architecture, but it was during the mid-twelfth century with the development of Gothic architecture that rose windows came into prominence.
During the Gothic period, the emphasis in church architecture was on soaring height and a greater sense of light. Taller window-filled churches were made possible by advances in building techniques such as supporting stonework in the form of bars or ribs between glass sections. Tracery allowed windows to become larger and more open, more decorative and elaborate, inside spaces to be more open and brighter.