Koryo Celadon remains one of the high points of world art. This Korean pottery style, which was at its peak in the 12th Century A.D., and called by the Chinese "one of the ten most wonderful things in the world," was a truly major achievement in the field of ceramics. Its most important element was its delicate green glaze, a secret formula now lost. As simple and elegant as Koryo Celadons appear, they were the result of intricate craftsmanship that often employed up to four inlays.