People's feelings towards nature are always in the contradiction of dependence and boredom. People need sunshine, but they don't like to be exposed to a large amount of dazzling light. In the high-density old city, people are eager for sunshine, but they don't know where to open the window. To reconcile this contradiction, we draw on the wisdom contained in the cold alleys in traditional houses in Lingnan area of China. While promoting ventilation, we guide light to the places where it is needed through the cold alleys. In this scheme, the cold lane is defined as a slit generated by the nesting operation of layers, and a window niche and stairs are arranged in the slit. These slits have different widths and the opening directions of the niches are different, so that light can be accurately guided to the corresponding indoor space when it is needed, and a light environment filled with diffused light which is most suitable for the corresponding activities of residents is created. In this way, the light in the space will be softer, and the sunshine intensity in the space will change with the passage of time, and people will move accordingly, looking for the most suitable place to go at that time and doing the most suitable thing. As a result, people's activities and sunlight, building space have established a link in life. We also hope that this model can be applied in high-density old cities to improve the quality of living environment in old cities.