Tourists hike in the Picos de Europa National Park in Spain, Aug. 21, 2019. (Xinhua/Guo Qiuda)

Tourists visit the village of Potes at the foot of Picos de Europa, Spain, Aug. 20, 2019. (Xinhua/Guo Qiuda)

A climber looks at the Picos de Europa National Park from the top of the mountain in Spain, Aug. 21, 2019. (Xinhua/Guo Qiuda)

Tourists take a rest in the Picos de Europa National Park in Spain, Aug. 21, 2019. (Xinhua/Guo Qiuda)

Photo taken on Aug. 20, 2019 shows the scenery of Picos de Europa National Park in Spain. (Xinhua/Guo Qiuda)

Photo taken on Aug. 21, 2019 shows the scenery of Picos de Europa National Park in Spain. (Xinhua/Guo Qiuda)