People visit a park reconstructed from sinkholes in a coal mining area in Guye District of Tangshan City, north China's Hebei Province, June 9, 2020. The distrist has been making continuous efforts in recent years to improve its ecological environment, which was once damaged by mining industry. (Xinhua/Mu Yu)

Aerial photo taken on June 9, 2020 shows a view of a park reconstructed from sinkholes in a coal mining area in Guye District of Tangshan City, north China's Hebei Province. The distrist has been making continuous efforts in recent years to improve its ecological environment, which was once damaged by mining industry. (Xinhua/Mu Yu)

People visit a park reconstructed from an area for coal washing in Guye District of Tangshan City, north China's Hebei Province, June 9, 2020. The distrist has been making continuous efforts in recent years to improve its ecological environment, which was once damaged by mining industry. (Xinhua/Mu Yu)

Aerial photo taken on June 9, 2020 shows a view of a lake reconstructed from sinkholes in a coal mining area in Guye District of Tangshan City, north China's Hebei Province. The distrist has been making continuous efforts in recent years to improve its ecological environment, which was once damaged by mining industry. (Xinhua/Mu Yu)

Aerial photo taken on June 9, 2020 shows a view of a park reconstructed from sinkholes in a coal mining area in Guye District of Tangshan City, north China's Hebei Province. The distrist has been making continuous efforts in recent years to improve its ecological environment, which was once damaged by mining industry. (Xinhua/Mu Yu)