Located on a hill near mileage 143 of the Provincial Highway 17 in Beimen District, it is said that it was the place where Xi ZHENG, the aunt of Cheng-kung ZHENG, was buried. Local residents call the mausoleum as the “Old Grandma’s Tomb”. It is said that to extinguish the lifeline of the Kingdom of Tungnin in Taiwan by means of fengshui (geomancy), the Qing government searched for the graves of the descendants of Cheng-kung ZHENG across Taiwan. To avoid the Qing government from digging the grave of the dead, descendants of Cheng-kung ZHENG specifically built nine identical graves on this hill called “Beimenyu” for distraction, decoying and diversion. As the hill is located near Taijiang inland sea and covered by mist from the sea’ surface, it is called the “misty grave”.