The towering sandstone pillars in central China that climb into the misty sky are renowned for their beauty, inspiring the alternate universe in the 2009 blockbuster “Avatar.”

       But in recent weeks, the national park of Zhangjiajie, the location of those stunning formations topped with pine trees, has become known for a sight far less appealing: mountains of trash.

       The government in Cili County in Hunan Province, which oversees the park, ordered a huge cleanup effort this month after videos posted by cave explorers of the garbage buildup spread widely.

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