Great Zimbabwe, 12th to the 15th century CE. Today, ruins in Zimbabwe dated from this period bear testimony to the earliest of the centralized kingdoms of Zimbabwe. It is estimated that the central ruins and surrounding valley (a combined area of some 2.8 square miles) supported a Shona population of 10,000 to 20,000. Their economy was based on cattle husbandry, crop cultivation, and the trade of gold on the coast of the Indian Ocean. Great Zimbabwe was the heart of a thriving trading empire from about AD 1100 to 1500.