Zhao's son Ning'er saw the letter 21 years after his mother's sacrifice as the letter was found in the Japanese military interrogation archives in 1957. The letter has moved countless visitors since the memorial hall was opened 65 years ago.

Another attraction on the mountain is the Thousand Buddha Temple, first built in the Tang Dynasty (618-907). It is home to 1,032 Buddhist statues, said the temple's abbot, Yang Dawei.

Every day, bell chimes echo through the dense forests of the mountain, giving testimony to the temple's millennia of history, ushering in a solemn atmosphere.

During the Labor Day holiday from May 1 to 5 this year, a record 140,600 people visited the mountain, up 11 percent over the same period last year, said Huang Hao, deputy director of the Cuiping Mountain scenic area management center.