Cat Ba's beautiful national park is home to 32 types of mammal, including most of the world's 65 remaining golden-headed langur, the world's most endangered primate. There are some good hiking trails here, including a hard-core 18km route up to a mountain summit.
To reach the park headquarters at Trung Trang, hop on the green QH public bus from the docks at Cat Ba Town (25,000d, 7am, 11am and 3pm), hire a xe om (around 80,000d one way) or hire a motorbike for the day.
A guide is not mandatory but is definitely recommended to help you make sense of the verdant canopy of trees. Most visitors opt to visit the park on an organised tour – Cat Ba Ventures runs good day-trips here – but you can also arrange guides with the rangers at the park headquarters. Within the park the multichambered Hang Trung Trang (Trung Trang Cave) is easily accessible, but you will need to contact a ranger to make sure it's open. Bring a torch (flashlight).
The challenging 18km hiking trail in the park takes six hours and is best done with a guide. Boat or bus transport to the trailhead and a boat to get back to town also need to be arranged. Again, rangers at the headquarters can help with this or speak to Cat Ba Ventures or Asia Outdoors in Cat Ba Town. Take proper hiking shoes, a raincoat and a generous supply of water for this hike. Independent hikers can buy basic snacks at the kiosks in Viet Hai (a remote minority village just outside the park boundary), which is where many hiking groups stop for lunch. This is not an easy walk, and is much harder and more slippery after rain. There are shorter hiking options that are less strenuous.
Many hikes end at Viet Hai from where taxi boats shuttle back to Ben Beo Pier (about 250,000d per boat). A shared public boat (50,000d per person) departs from Ben Beo at 11am, and from Viet Hai at 7am.
Of the mammals present in the park, the more commonly seen include macaques, deer, civets and several species of squirrel, including the giant black squirrel. Seventy bird species have been spotted here, including hawks, hornbills and cuckoos. Cat Ba also lies on a major migration route for waterfowl that feed and roost on the beaches in the mangrove forests. Over a thousand species of plant have been recorded in the park, including 118 trees and 160 plants with medicinal value.