hunan zhangjiajie national forest park yangjiajie longquan gorge cliffs like a spectacular `ancient city wall`

ancient bare barrier canyon city cliff cluster color daytime environment erosion fog forest geology gorge green karst landscape limestone longquan lush mist mountain mountains national nature oriental outdoor park peak photography plant reserve rock rocky sandstone scenery sky spectacular steep stone structure tranquil travel trees vacation valley virgin wall weathered woods zhangjiajie