Underwater museum reopens in SW China Visitors look at the inscriptions engraved on the stone ridge through an electronic screen at Baihel...

Underwater museum reopens in SW China

Visitors look at the inscriptions engraved on the stone ridge through an electronic screen at Baiheliang Underwater Museum in southwest China's Chongqing Municipality, March 28, 2012. (Xinhua/Liu Chan)

A visitor take photos of stone ridge through the window at Baiheliang Underwater Museum in southwest China's Chongqing Municipality, March 28, 2012.(Xinhua/Liu Chan)

A foreign visitor shows a souvenir with seals on it at Baiheliang Underwater Museum in southwest China's Chongqing Municipality, March 28, 2012.(Xinhua/Liu Chan)

Visitors look at the fish sculpture at Baiheliang Underwater Museum in southwest China's Chongqing Municipality, March 28, 2012. (Xinhua/Liu Chan)

The Baiheliang Underwater Museum, unveiled in 2009, reopened to the public earlier this month after months of reconstruction.

The museum, built about 40 meters below surface in the upper reaches of the Yangtze River off the coast of Fuling, Chongqing Municipality, protects a reef created about 1,200 years ago to measure the changes in water levels.

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 (618-907) 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.