For one of the best views in Vietnam – no, we’re not kidding – head to Cannon Fort where there are astounding panoramas of Cat Ba Island's jungle-clad hills rolling down to colourful tangles of fishing boats in the harbour and out to the karst-punctuated sea beyond.
The entrance gate is a steep 10-minute walk from Cat Ba Town and from the gate it's another stiff 20-minute walk to the fort, or take a xe om from Cat Ba Town (15,000d).
Well-labelled paths guide visitors past underground tunnels, and two well-preserved gun emplacements (one ‘manned’ by life-size Viet Minh mannequins), out to two viewpoints overlooking the island. There's even a cafe (with more great views from its terrace) and a tiny museum.
The tunnels and gun emplacements here were first installed by the Japanese in WWII, but were also utilised by the French and Vietnamese during subsequent conflicts.