People travel in a subway train, which is turned into a temporary museum to celebrate the upcoming National Day in Chengdu, southwest China's Sichuan Province, Sept. 18, 2019. More than 300 historic photos and pictures of historic items were on display in the museum set up in a subway train, showcasing the great changes in China, especially in Sichuan Province and Chengdu City, over the past 70 years. (Photo: Xinhua)

Media reporters work in a subway train, which is turned into a temporary museum to celebrate the upcoming National Day in Chengdu, southwest China's Sichuan Province, Sept. 18, 2019. More than 300 historic photos and pictures of historic items were on display in the museum set up in a subway train, showcasing the great changes in China, especially in Sichuan Province and Chengdu City, over the past 70 years. (Photo: Xinhua)

A passenger takes photos in a subway train, which is turned into a temporary museum to celebrate the upcoming National Day in Chengdu, southwest China's Sichuan Province, Sept. 18, 2019. More than 300 historic photos and pictures of historic items were on display in the museum set up in a subway train, showcasing the great changes in China, especially in Sichuan Province and Chengdu City, over the past 70 years. (Photo: Xinhua)

Passengers take photos in a subway train, which is turned into a temporary museum to celebrate the upcoming National Day in Chengdu, southwest China's Sichuan Province, Sept. 18, 2019. More than 300 historic photos and pictures of historic items were on display in the museum set up in a subway train, showcasing the great changes in China, especially in Sichuan Province and Chengdu City, over the past 70 years. (Photo: Xinhua)