Building images of the past

Another reason Zhao keeps locations secret is that most of the places she visits are dilapidated, which may pose a danger to people who are not well prepared.

Zhao once had scrapes and bruises after falling through a rotted wooden stage while exploring an abandoned theater.

"For safety concerns, I seldom go to these places alone and never go at night," she says, adding that she always asks for permission before entering these buildings.

To identify potentially promising sites, she usually uses satellite maps for clues, because these locations are marked in dark gray.

"I have an ambitious plan to document every derelict structure in China and talk with locals about the stories behind them," Zhao says.