What can a smile tell us about a city?

An American historian travels to Luoyang, one of China's ancient capitals, in search of the "smile" his students told him about. From the serene expression of the Vairocana Buddha at the Longmen Grottoes to the famous hand-holding figurines at the Luoyang Museum, he discovers stories of cultural exchange, preservation, friendship and human connection that have endured for more than 1,500 years.