A visitor looks out from a window at Baiheliang Museum, China's first underwater museum built about 40 meters below surface in the upper reaches of the Yangtze River off the coast of Fuling City, southwest China's Chongqing Municipality, Feb. 21, 2021. (Xinhua/Liu Chan)

Baiheliang Museum reopened to public recently after a four-month renovation. Baiheliang, literally "White Crane Ridge", is a 1,600-meter-long and 25 meter-wide smooth stone ridge engraved with inscriptions about China's longest river, dating from 763 in the Tang Dynasty to the early 20th century. On the huge rock are 20 fish sculptures that serve as water-level markers and about 30,000 characters of Chinese poems from different dynasties. It is claimed to be the world's oldest hydrographic survey device and is one of the four state-level national treasures in the Three Gorges area.

 

Photo taken on Feb. 21, 2021 shows the protected reef created about 1,200 years ago to measure the changes in water levels at Baiheliang Museum, China's first underwater museum built about 40 meters below surface in the upper reaches of the Yangtze River off the coast of Fuling City, southwest China's Chongqing Municipality. (Xinhua/Liu Chan)

 

People visit an on-land exhibition room of Baiheliang Museum, China's first underwater museum built about 40 meters below surface in the upper reaches of the Yangtze River off the coast of Fuling City, southwest China's Chongqing Municipality, Feb. 21, 2021. (Xinhua/Liu Chan)

 

People visit Baiheliang Museum, China's first underwater museum built about 40 meters below surface in the upper reaches of the Yangtze River off the coast of Fuling City, southwest China's Chongqing Municipality, Feb. 21, 2021. (Xinhua/Liu Chan)