During periods of conflict, a field hospital was built and put into use inside a mountain within Cat Ba National Park.
Situated roughly eight km away from Cat Ba town, it takes about 30 minutes to travel to the Hospital Cave by motorbike.
The cave can easily be found by following the signs along the road.
The three-metre wide entrance is located halfway up the mountain, meaning visitors must climb up a wooden staircase.
Previously, the cave was named after Hung Son, a military general who served during the era of the Tran Dynasty. He is said to have been the first person to have discovered this cave in the 13th century.
From 1963 to 1965, as the American War escalated, a field hospital was established in order to treat wounded soldiers and shelter them from attacks. Following this, local people started to refer to it as the 'Hospital Cave'.
This hospital has about 17 rooms for patients along with a number of other rooms for doctors.
It also has a physical recovery room, meeting room, a kitchen room, a medicine room, and a weapons room.
When operational the hospital had been able to accommodate about 200 soldiers.
The stairs to the second floor where a cinema room is set up.
The emergency exit is a huge water tank which leads to the lower floors.
Entrance tickets to the cave cost VND40,000 per adult and VND20,000 per child.