ナショナルジオグラフィックさんのインスタグラム写真 - (ナショナルジオグラフィックInstagram)「Photo by Robbie Shone @shonephoto | The limestone in this region of China is so strong it can withstand giant voids like Cloud Ladder Hall. Eventually though, over time, the weight of rock above will become too great and it will collapse, forming a giant sinkhole or Tian Keng, a huge hole open to the surface. This gigantic cave that has never seen the light of day is a tough photography target, even in clear conditions. But this one posed an extra challenge: it's so large and isolated that it has its own weather–including clouds. Weather makes its way in, but it can't make its way out. For this photograph, I had three accomplices: one standing out of frame with a large, single-use flashbulb, one standing on the rock to the left shining her headlamp at the cave wall, and a third dangling from a rope hundreds of meters away. Although the shutter was open for only 30 seconds, the whole operation took four hours, with the team communicating via walkie-talkie because the echoes made shouting unworkable.」6月24日 4時49分