A kingdom traditionally dated 57 BC-668 AD, the oldest of the monarchies of the Three Kingdoms period, and including the Unified or Great Silla period of 668-935, the golden age of Korean art. It eventually came to cover most of southeastern Korea east of the Naktong River. The original territory of the Silla kingdom, the modern North Kyongsang province, is a mountain-secluded triangle. Silla was in competition with the Koguryo and Paekche until 668 and had relations with Japan's Yamato. When it unified in 668, its capital remained in Kyongju. At that site are large mounded tombs of the 5th-6th centuries with fine gold work. It became a gridded city in the 7th century and the Anapchi pond was built.