Aerial photo taken on Oct. 19, 2019 shows scenery of Heicheng relic site in Ejina Banner, north China's Inner Mongolia Autonomous Region. (Xinhua/Peng Yuan)
Aerial photo taken on Oct. 18, 2019 shows a view of Heicheng relic site in Ejina Banner, north China's Inner Mongolia Autonomous Region. (Xinhua/Peng Yuan)
Photo taken on Oct. 19, 2019 shows a view of Heicheng relic site in Ejina Banner, north China's Inner Mongolia Autonomous Region. (Xinhua/Peng Yuan)
Photo taken on Oct. 18, 2019 shows a view of Heicheng relic site in Ejina Banner, north China's Inner Mongolia Autonomous Region. (Xinhua/Peng Yuan)
Photo taken on Oct. 18, 2019 shows a view of Heicheng relic site in Ejina Banner, north China's Inner Mongolia Autonomous Region.(Xinhua/Peng Yuan)
Aerial photo taken on Oct. 19, 2019 shows scenery of Heicheng relic site in Ejina Banner, north China's Inner Mongolia Autonomous Region. (Xinhua/Peng Yuan)
Photo taken on Oct. 18, 2019 shows a view of Heicheng relic site in Ejina Banner, north China's Inner Mongolia Autonomous Region. (Xinhua/Peng Yuan)
A tourist visits Heicheng relic site in Ejina Banner, north China's Inner Mongolia Autonomous Region, Oct. 18, 2019.(Xinhua/Peng Yuan)