Fisherman finds valley, then loses it
A Wuling fisherman follows a stream through a grove of blossoming peach trees to a narrow cave opening, squeezes through, and finds a fertile valley whose villagers descend from refugees who fled Qin-dynasty chaos and never heard of the Han, Wei, or Jin. They host him, and as he leaves they ask him not to speak of them to outsiders. He marks his route anyway and reports to the prefect, but the search party cannot find the valley again, and a later seeker, Liu Ziji, dies before he can try.