Archaeologists digging in the medieval city of Great Zimbabwe have discovered pieces of jade-green Chinese pottery, suggesting that the enigmatic empire had long-distance connections with East Asia more than 1,000 years ago. Great Zimbabwe, located in the southeastern part of modern-day Zimbabwe, was the capital of an ancient empire that arose in southeastern Africa in around A.D. 1000. Little is known about this precolonial empire because its people did not leave a written history, but new archaeological excavations are shining a light on the enormous scale of the centuries-old civilization known for its intricate metalworking and ritual stone carvings.In the new PBS documentary "Secrets of...