Tourists go sightseeing on a transparent horseshoe-shaped cantilever bridge at the Yunyang Longgang Geological Park, one "natural oxygen bar," in Chongqing, southwest China, April 14, 2018. As more and more Chinese people are choosing to visit places that have fresh air, thick forests and are rich in negative ions, ecotourism becomes a fresh favoured choice across the country. According to a report by the China Meteorological Service Association, trips to the regions granted as "natural oxygen bars" by the association surged over 200 percent year on year in 2018. (Xinhua/Wang Quanchao)