The cave, about 14km southeast of the city of Ha Long, attracts tourists both with a famous romantic legend and impressive scenery. Couples consider it a lucky place to declare vows of love.
Trinh Nu Cave is associated with a touching love story about a beautiful girl from a poor fishing family who was sent to serve as a concubine for a rich administrator of the local fishing zone. She refused because she already had a boyfriend, who at that time was offshore catching fish to prepare for their wedding. The administrator, angered by her refusal, exiled her to a wild island where she suffered hunger and exhaustion. On one frightening night of terrible rain and winds, she turned to stone.
Meanwhile, her lover, rowed his boat to search for her but the tempest destroyed his boat. In a lighting flash he saw his mate in the distance, but his calls were driven away by the wind. He used a stone block to hammer the mountain cliffs to announce to her that he was nearby, but exhausted and bleeding, he too turned to stone.
Both can still be seen by the hundreds of tourists who visit the popular site daily. On entering the cave, a stone statue of a long-haired girl seems to be looking out to sea in vain hope. Situated opposite Trinh Nu Grotto, Trong (or male) Grotto has a stone statue of a boy turning his face to Trinh Nu Grotto.
Trinh Nu Grotto has three chambers. The tallest ceiling is about four meters high. The third chamber is the biggest – 60 meters long, 20 meters wide. Lights installed in the spacious cave make the stalagmites and stalactites sparkle. Some call to mind a lady with long hair looking out to the ocean. Others appear to glisten like hanging chandeliers.
Most of the stalagmites and stalactites have stopped developing, yet a few are still growing in the second compartment, where cracks still allow raindrops to seep in.
In addition to legend, the cave is of archaeological importance. Here, archaeologists have discovered many pieces of porcelain with decorative patterns, vestiges attesting to prehistoric habitation in the area. The cave is 5-10m above sea level. Fronting the northwest gate is a beach made of sand mainly and animal shells. Scattered on the beach are massive stones covered by moss.
In the third compartment towards the northeast gate, limestone blocks have collapsed due to a large underground stream, which abraded and dissolved the stone.