Fallen leaves are seen at the Royal National City Park in Stockholm, Sweden, Oct. 12, 2019. (Xinhua/Zheng Huansong)

Fallen leaves are seen at the Royal National City Park in Stockholm, Sweden, Oct. 12, 2019. (Xinhua/Zheng Huansong)

Fallen leaves are seen at the Royal National City Park in Stockholm, Sweden, Oct. 12, 2019. (Xinhua/Zheng Huansong)

Fallen leaves are seen at the Royal National City Park in Stockholm, Sweden, Oct. 12, 2019. (Xinhua/Zheng Huansong)

A man and a dog walk at the Royal National City Park in Stockholm, Sweden, Oct. 12, 2019. (Xinhua/Zheng Huansong)

The autumn scenery of the Royal National City Park is seen in Stockholm, Sweden, Oct. 12, 2019. (Xinhua/Zheng Huansong)

Fallen leaves are seen at the Royal National City Park in Stockholm, Sweden, Oct. 12, 2019. (Xinhua/Zheng Huansong)

Fallen leaves are seen at the Royal National City Park in Stockholm, Sweden, Oct. 12, 2019. (Xinhua/Zheng Huansong)