A trouper makes preparation for the performance of "gaoshan" opera in Guanyinba village of Yulong township in Longnan, Northwest China's Gansu province, Feb 6, 2017. "Gaoshan" opera, which originated in Yulong, has a history of about 700 years. It was listed as one of the national intangible cultural heritages in 2008. [Photo/Xinhua]