Aerial photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Aerial photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Tourists visit the Mutianyu Great Wall in Beijing, capital of China, on Oct. 24, 2020. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Aerial photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Tourists visit the Mutianyu Great Wall in Beijing, capital of China, on Oct. 24, 2020. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Aerial photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Aerial photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Aerial photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Aerial photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Aerial photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Tourists visit the Mutianyu Great Wall in Beijing, capital of China, on Oct. 24, 2020. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)

Photo taken on Oct. 24, 2020 shows a view of the Mutianyu Great Wall in Beijing, capital of China. The Mutianyu Great Wall is a major tourist attraction for autumn views in Beijing. (Xinhua/Ju Huanzong)