The Qingshuitang area of Zhuzhou, Hunan province, was once known as a place with gray skies, black chimneys, blanched waters and the pungent odor of sewage. 

The 15.15 square-kilometer area, once had 261 enterprises, most of which were heavy industrial plants. The area's annual production value was almost 30 billion yuan ($4 billion) and boasted more than 160 "firsts" in China's industrial history, including the country's first generation of locomotives and aircraft. 

More than 200 chimneys soaring into the sky were erected there, with the tallest reaching 133 meters. It was built by Zhuzhou Smelter Group in the 1950s and was the tallest chimney in Asia at the time. 

However, the economic boom also took a toll on the local environment. The emission of gas into the air and pollutants into the water of Qingshuitang accounted for two thirds of the total in Zhuzhou. It was one of the most heavily polluted industrial areas in the country in the 2000s, and Zhuzhou was one of the heaviest polluted cities in China. 

In 2014, Qingshuitang was listed as a pilot area for the relocation of industries and the transformation of old urban industrial areas nationwide.

To completely cut off pollution sources, the city relocated and renovated the industrial zone, shutting down all 261 enterprises by the end of 2018.

Zha Changmiao, general manager of the Corporate Culture Department and Director of the News Center of China Communications Construction Co, said the company is in charge of building an urban park in Qingshuitang, with a total investment of 940 million yuan ($128 million). 

The company also built the Qingshuitang Bridge, which opened in August and has been dubbed by residents as the most beautiful bridge on the Xiangjiang River, an important artery of the Yangtze River, he said. 

The bridge is a double-layer steel truss arch design, with the upper layer consisting of a dual six-lane road and the lower layer serving as a pedestrian passage, Zha said. 

Xu Feifei, director of the commercial service center of Zhuzhou Qingshuitang Investment Group, said Qingshuitang, which is located on the north bank of the Xiangjiang River and serves as the geographical center of the Changsha-Zhuzhou-Xiangtan city cluster, is well-connected by major highways and two major railway arteries. 

Qingshuitang is actively transforming itself from an old industrial center into area with modern intelligent manufacturing, science and innovation, she said. It has attracted well-known enterprises such as the CRRC Zhuzhou's Carbon Neutrality Industry Park and Sany Group's new energy petroleum equipment headquarters, Xu said.