There is a 290-meter deep karst sinkhole near the village of Luoquanyan in Xuan'en county, southwestern Hubei province. The naturally formed limestone cavity is nothing but a botanical delight. Due to its undisturbed location and favorable growing conditions, the sinkhole has developed a thriving ecosystem that was hidden from the public’s eye. Although the sinkhole was discovered decades ago, only a handful of people have ever plumbed its difficult-to-reach depths. (Photo/Xinhua/Song Wen)