Invisible from both road and air, Hospital Cave was strategically important in the Vietnam-American War.

Built from 1963-65 with the help of the Chinese, the concrete bombproof cave was laid out over three stories; the bottom two acted as a hospital where soldiers could rest, recuperate and relax, and the tiny third floor acted as a safe house for Viet Cong leaders. The shelter was equipped with access to fresh water and ventilation shafts, and there are even escape tunnels ready for the event of a quick getaway. 

Hospital Cave was abandoned in 1975, but in recent years has become a popular attraction on Cat Ba, where English-speaking guides show visitors around, fully justifying the extremely cheap 15,000 dong entrance fee. Although the rooms are now empty, it’s possible to see the how the Hospital was once set up. It includes an operating theatre, doctors office, several recovery rooms, and a huge natural cavern that was used as a cinema room.