Now we continue the second season of our series Tides of Change. Our team of reporters brings you stories along China's coast. Today we visit the southeastern city of Quanzhou. It was designated a UNESCO World Heritage Site this year. Quanzhou was an important trade and cultural hub in Chinese history. Yang Chengxi tells us more.

This quiet city called Quanzhou was in fact the most important seaport in China from the 9th to the 14th century. To give you a sense of just how famous it was, medieval explorer Marco Polo called it the "Alexandria of the East". Arab explorer Ibn Battuta wrote this when he came here in 1346: "When we had crossed the sea the first city to which we came was Zaitun…"

YANG CHENGXI Quanzhou "The Arabs called this place Zaitun because back then, locals planted a kind of red-flowered trees called Ci Tong in Chinese across the city. The foreign sailors who entered through ancient ports like this one here were so impressed they named the city after it. Now back to the quote."

Its harbor is among the biggest in the world, or rather is the biggest; I have seen about a hundred big junks there, and innumerable little ones.

YANG CHENGXI Quanzhou "The 'junks' he was referring to, are probably these."

The remains of this commercial vessel were found in Quanzhou in the 1970s. It was built in the 13th century.

WU QIUWEN Deputy Director, Publicity Department Quanzhou Maritime Museum "The ship was returning from Southeast Asia as it was loaded with spices, medicine, and other merchandise."

Merchants in Quanzhou traded with others like Indians, Persians, Europeans, and Arabs. The city was so essential to China's foreign trade, that imperial records from the time use Quanzhou as the zero mile for distances between China and foreign countries, making it the starting point of the ancient maritime silk road.

With the influx of goods, came many cultures. This is an ancient Buddhist temple, with Hindu decorations. These are Christian angels with oriental facial features. Here is a temple built by ancient Ceylonians and, this temple hosts the world's only stone statue of Mani, the prophet of Manichaeism, a once-thriving religion that has now faded away.

CHEN YINGYAN Deputy Head, Quanzhou Maritime Museum "The Quanzhou Maritime Museum hosts over 400 carved stone monuments, from Christian and Hindu to Islamic. The most prominent groups were the Arabs and Persians."

Historically, Quanzhou's role as China's biggest sea port ended after the fourteenth century and soon fell into marginalized obscurity. But ironically, it was because of this relatively sudden decline, that left many of the remains untouched for centuries and allowed for modern historians' analyses. YCX, CGTN, Quanzhou, Fujian Province.