We discussed the formative nature of a city square reffered to be the frame of creating environment in the this study. We raised a question that the place, the size and the form of a city square are out of harmony with a surrounding environmental condition, and examined the functional effect and the formate value of a sunken square at the same time. We got hold of the special shape and the specific character, the distinctive structure, and the influence of the minute temperature of a cuty aquare, and showed the improved direction how to make them better focusing on the target square of a cosmopolitan city of Seoul. Finally, to correct the above-mentioned problems, we emphasized the our traditional city square which is reffered to have a peculiar property, and proposed that a public institutuion should develope the city square, and should make an effort to reflect the design based on the scientific experiment.