What is the defining feature of a rose window?

The defining feature of a rose window is that it is a circular stained-glass window, which is prominently found in Gothic cathedrals and churches. These windows are characterized by their intricate designs, often featuring patterns, biblical scenes, or symbolic imagery arranged in a radial symmetry radiating from the center. The use of vibrant colors and diverse glass pieces in rose windows not only serves an aesthetic purpose but also plays a significant role in storytelling and the illumination of religious spaces. The circular shape itself is symbolic of eternity and the divine, making rose windows a powerful architectural and artistic element in sacred spaces.

The other options do not capture the essence of a rose window, as they describe features that do not embody the visual or symbolic qualities associated with this specific type of architectural element.