The Silk Road was an ancient network of trade routes that were central to cultural interaction between China and Europe. Chinese governments, starting with the Han Dynasty, provided protection on the western edges of China to merchants and trade caravans travelling the Silk Road. High-value goods, including silk, sugar, porcelain, and spices, made their way across central Asia. This international exchange of goods also facilitated the diffusion of scientific, religious, and artistic advancements. The great trade cities became the center of cultural diffusion spreading ideas across continents.