During this period, Ife (also known as Ile-Ife), the cradle of contemporary Yoruba culture, is the center of some of the richest artistic traditions of the Guinea Coast. Situated in the West African forest, Ife is the center of a trading network that capitalizes on its accessibility from the Niger and several smaller rivers, from the West African coast, and from the savanna country to the north. Stone monoliths are characteristic of early Ife art, while in the latter half of the first millennium A.D., distinct styles of finely modeled terracotta representations and works in cast metal are developed and refined. This period is also significant for the emergence of lost-wax casting. While the smelting of metallic ores dates to the first millennium B.C., and by about 1000 A.D. iron and copper smelting techniques have spread throughout the continent, the complex technique of lost-wax casting begins to be practiced only in the tenth century. This method of producing exquisitely refined brass works is first employed along the Guinea coast at Igbo-Ukwu, a region populated by Igbo peoples.