Aerial photo taken on June 14, 2020 shows the scenery of the Zishan Park in Congtai District of Handan, north China's Hebei Province. Transformed from an area with over 40 abandoned coal mines, Zishan Park has been upgraded in recent years through ecological restoration and landscape enhancement. (Xinhua/Zhu Xudong)

Aerial photo taken on June 14, 2020 shows the scenery of the Zishan Park in Congtai District of Handan, north China's Hebei Province. Transformed from an area with over 40 abandoned coal mines, Zishan Park has been upgraded in recent years through ecological restoration and landscape enhancement. (Xinhua/Zhu Xudong)

Aerial photo taken on June 14, 2020 shows the scenery of the Zishan Park in Congtai District of Handan, north China's Hebei Province. Transformed from an area with over 40 abandoned coal mines, Zishan Park has been upgraded in recent years through ecological restoration and landscape enhancement. (Xinhua/Zhu Xudong)

Aerial photo taken on June 14, 2020 shows the scenery of the Zishan Park in Congtai District of Handan, north China's Hebei Province. Transformed from an area with over 40 abandoned coal mines, Zishan Park has been upgraded in recent years through ecological restoration and landscape enhancement. (Xinhua/Zhu Xudong)

Aerial photo taken on June 14, 2020 shows the scenery of the Zishan Park in Congtai District of Handan, north China's Hebei Province. Transformed from an area with over 40 abandoned coal mines, Zishan Park has been upgraded in recent years through ecological restoration and landscape enhancement. (Xinhua/Zhu Xudong)

Aerial photo taken on June 14, 2020 shows the scenery of the Zishan Park in Congtai District of Handan, north China's Hebei Province. Transformed from an area with over 40 abandoned coal mines, Zishan Park has been upgraded in recent years through ecological restoration and landscape enhancement. (Xinhua/Zhu Xudong)

Aerial photo taken on June 14, 2020 shows the scenery of the Zishan Park in Congtai District of Handan, north China's Hebei Province. Transformed from an area with over 40 abandoned coal mines, Zishan Park has been upgraded in recent years through ecological restoration and landscape enhancement. (Xinhua/Zhu Xudong)

A visitor poses for a selfie at the Zishan Park in Congtai District of Handan, north China's Hebei Province, June 14, 2020. Transformed from an area with over 40 abandoned coal mines, Zishan Park has been upgraded in recent years through ecological restoration and landscape enhancement. (Xinhua/Zhu Xudong)