The peninsula of North and South Korea has historically been the political and cultural conveyor between Japan and China, the two great powers surrounding it. Despite the intermingled language, history and people, Korea has native artistic traditions that influenced its neighbors. Perhaps the most important of these accomplishments is Korean porcelain and earthenware. In the 12th century, during the Koryo period, Korean potters began producing celadon wares. The distinctive bluish green glazes and incised designs captivated Chinese collectors, who declared celadon one of the ten wonders of the world. Another distinguishing feature of celadon is the form and shape of the vessels. Koryo pieces are considered masterpieces by merit of the marriage of form and function alone. The proximity of the Korean peninsula and the Nagasaki area of Japan encouraged great migrations of artisans to settle in Japan. With them they brought their remarkable stoneware technologies. The Japanese were smitten with the pottery of the Korean artists, and adopted much of it into their own growing traditions, culminating in the highly ritualized Tea Ceremony of the fifteenth and sixteenth centuries.