People's feelings for nature are always in the contradiction of dependence and boredom. People need sunshine, but they don't like being in a lot of dazzling light. In the high-density old city, people are eager for sunshine, but they don't know where to open the window.In order to reconcile this contradiction, we learn from the wisdom contained in the cold lane of traditional houses in the south of the five ridges in China. While promoting ventilation, we guide the light to the place where it is needed through the cold lane.In this scheme, the cold lane is defined as the slit produced by the nesting operation of layers, in which window niches and stairs are set. The width of these slits is different, and the opening direction of the niche is also different, so that the light can be precisely guided to the corresponding indoor space at the time when it is needed, and create the most suitable light environment full of diffuse light for the corresponding activities of the residents. 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 and doing the most suitable thing. Thus, people's activities, sunlight and architectural space have established a kind of life connection.We also hope that this mode can be applied in the high-density old urban area, and improve the quality of the living environment in the old urban area.