at night, at the coordinates: "640, -1184" you will see light in an area, but no light source producing it. I have tried removing the land, and i have looked all around but i do not see any light sources close enough to produce it.
Sometimes the lighting glitches and leaves light behind when a light source is removed. This is especially common when I regenerate an area. If you can find the brightest part and place a magic light and remove it then it often fixes it.