Chu Pansheng's memory of his hometown in Qingshuitang, Central China's Hunan province, resembles that of London depicted in the novels of Charles Dickens, which was filled with smoke, soot and foul odors, caused by the First Industrial Revolution.

The Qingshuitang area of Zhuzhou was once known as a place with gray skies, smoke-belching chimneys, bleached waters and the pungent odor of sewage, Chu said.

The area covering 15 square kilometers once had 261 enterprises, most of which were heavy industrial plants.

The annual production value of the area used to be almost 30 billion yuan ($4 billion) and it boasted more than 160 "firsts" in China's industrial history, such as manufacturing the country's first locomotive and aviation engines.

More than 200 chimney stacks were erected there, with the tallest at 133 meters built by Zhuzhou Smelter Group in the 1950s, which was the tallest chimney in Asia at that time.

However, the economic boom took a toll on the local environment, with Qingshuitang becoming one of the most heavily polluted industrial areas in the country.

Chu's family moved to Qingshuitang in 2004 when he was 16, and his parents ran a small shop near the industrial plants.

"People living in other places of Zhuzhou didn't want to come here as it was known as a place with a gray sky, smelly smoke and dust everywhere," he said.

In 2014, Qingshuitang was listed as one of the pilot areas for the relocation and transformation of old industrial bases in urban areas nationwide.

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 Company, said the company is in charge of building an urban park in Qingshuitang, with a total investment of 940 million yuan.

Qingshuitang is actively transforming itself from an old industrial center into an area with modern intelligent manufacturing, science and innovation development, said Xu Feifei, director of the commercial service center of Zhuzhou Qingshuitang Investment Group.

It has attracted well-known enterprises such as CRRC Zhuzhou's Carbon Neutrality Industry Park and Sany Group's new energy petroleum equipment headquarters, Xu said.

Li Jun, a retired worker of Zhuzhou Smelter Group, has lived in Qingshuitang for more than 30 years.

"People did not dare to open the windows and everything in the house was covered by black dust even though the windows were closed," he said, speaking of the past.

The heavy pollution also took a toll on people's health, as many workers at the plants in Qingshuitang died before they were 70, and some children were born with birth defects, he said.

"Nowadays, the environment is much better and we don't need to worry about constantly mopping off the black dust and cleaning the apartment floor.

"Some of the chimneys in Zhuzhou are still there as a symbol of its heavy industrial past, but we should also look to the future as a city with high-quality development and a much better environment," he said.