Grandpa's Mountain City Password

Grandpa's old house was about to be demolished. Li Buyan went back to clean out his things and found a yellowed old map of Chongqing in the pillow compartment. There were no place names on it, just a few lines of a jingle he had grown up hearing. That was what his grandfather read to him when he was put to sleep. It is also something that grandpa has hidden all his life. Three Chongqing losers with a combined savings of less than 50,000 yuan, relied on a hand-drawn map, a few dialect children's songs, and their own unremarkable skills to get into the city's underground secrets for 86 years. There are writings in the air-raid shelter, hidden compartments in the ropeway station, and wartime code books hidden in the mezzanine of the teahouse at Ciqikou - the further they go in, the more people are staring at them. Later, Li Buyan learned that what his grandfather was looking for was not a treasure.