The Trinh Nu Grotto or Virgin Grotto is situated on the island range of Bô Hon in the system comprising the Sung Sôt Grotto, Dong Tiên Lake and Luon Grotto. It is 15 km south of Bai Cháy Beach. For fishermen, the Virgin Grotto is their house, but for young lovers, it is considered as the symbol of truly love, and is the romantic place for taking oath of love.