Liu Hengwu (right) measures the stone fragment with his student. [Photo/Yongpai App]

A newly identified stone fragment at Ningbo's Tiantong Temple may provide the first physical evidence that a medieval Buddhist stupa type associated with Japan's Satsuma towers was originally produced in China's coastal Zhejiang region.

According to a researcher from Ningbo University, a carved stone piece discovered at a temple site outside Ningbo city is likely part of a 13th-century Buddhist reliquary tower, long theorized to be the Chinese prototype of stone stupas later found in Japan's Kyushu region.

Liu Hengwu, a scholar who has spent years studying maritime cultural exchanges along China's historic Maritime Silk Road, identified the fragment during a field survey in April. The object had previously been catalogued as a generic architectural column.

He argues the piece matches the structure of so-called "stupa-style stone towers", known in Japan as Satsuma towers — named after the former Satsuma domain in southern Kyushu, where many examples were first recorded. Many researchers believe these towers were introduced from China during the Song and Yuan dynasties (960-1368).

The fragment, made of local Meiyuan stone, features carved guardian figures and a hollow structural design consistent with known examples found in coastal Zhejiang and Fujian, as well as surviving towers in places such as Quanzhou.

According to Liu, its form suggests a date in the late 13th century, a transitional period during which such towers evolved from taller, cylindrical designs into shorter, wider forms.

If confirmed, the discovery would be the first in the Ningbo urban area to link this stupa tradition directly to its production site, strengthening the argument that these stone towers were manufactured locally and shipped to Japan as part of maritime Buddhist exchange networks during the Song era.