The maritime trade network that connected China with Southeast Asia, India, the Persian Gulf and East Africa is older than the overland Silk Road — Han-dynasty texts describe Roman embassies arriving by sea, and Chinese silk reaches Egyptian tombs as early as the first century CE. Through the Tang, Song and Yuan dynasties the maritime corridor's importance grew; under the Yuan it likely surpassed the overland route, with Marco Polo describing Quanzhou as the largest port in the world.
The trade brought ceramics out — Longquan celadon, Jingdezhen blue-and-white — and gold, ivory, gemstones, frankincense and ideas back. The visible legacy is religious: the earliest mosques in China sit at these four ports (Guangzhou's Huaisheng claims the foundation date 627 CE), Christian and Hindu remains survive at Quanzhou, and the cosmopolitan trading communities left genealogies, gravestones and language traces still being decoded today.
UNESCO inscribed Quanzhou as 'Emporium of the World in Song-Yuan China' in 2021, recognising the city's role at the network's medieval peak. The port itself silted up after the 14th century — Quanzhou today is a heritage city rather than a working harbour — but the surviving mosques, temples, and stone inscriptions remain among the most diverse single-city religious complexes in East Asia.
For the visitor: Quanzhou is the canonical maritime-Silk-Road visit and the easiest case to make as a destination in itself; Guangzhou is the largest of the four but its medieval material is mostly absorbed into the modern city and harder to read. Ningbo and Yangzhou are best paired with the Yangtze Delta cluster (Suzhou, Hangzhou, Shanghai). All four are within a two-hour HSR ride of a major airport.