This extremely beautiful grotto is lying 9km west of Cam Pha Town and 20km from Bai Chay Beach. Hang Hanh is one of the longest grottoes in Halong Bay. It is 1,300m long and stretches throughout the stone mountain of Quang Hanh. The French named it “Le Tunnel” or Tunnel Grotto. The mouth of the grotto is so low one has to go by small boat to pass through.

To get there, visitors can hire canoes in Doan Wharf (Hon Gai, Halong City) or take a coach to Cam Pha. At the Cam Pha wharf, one can also hire boats or canoes to go to the grotto. One should visit the grotto at low tide, as this is the time the mouth of the grotto appears. Remember to bring along torches before starting the journey. It takes one some 60 to 90 minutes to complete the trip. Hang Hanh Grotto seems suitable for adventures. Another matter of no less important is that the boatmen must be experienced or else you will get locked up in this deep “Palace”.

In front of the present-day mouth stands Ba Co (Three Girls) shrine in a towering piece of stone. Legend has it that: “Once upon a time there were three girls who often went to the sea together. One day, they caught a pouring rain and took shelter in a grotto. They found the scenery so captivating that they forgot the time of rising tide. Locked up in the grotto, they passed away and became Water God.” Today fishermen usually went to the shrine to pray for their bestowing favours on them.