The Heaven Gate, Cổng Trời in Vietnamese, is the pass above Quản Bạ, where the road tops a ridge at about fifteen hundred metres and the whole Dong Van Karst Plateau opens beneath it. Below, a valley of green rice terraces and small fields is dotted with the humped outlines of limestone hills, and in the middle sits the pair of round green mounds known as Núi Đôi, the Twin Mountains, which local people call the Fairy's Bosom. On a clear morning, mist lies in the hollows and the hills float above it.
This is the far north of Vietnam, a few kilometres from the Chinese border, and the country is mountain, rock and weather. The Dong Van Karst Plateau is a UNESCO Global Geopark, recognised in 2010, a high landscape of grey limestone, deep gorges and ancient fossils, and it is home to a mosaic of ethnic groups, including the Hmong, Tay, Dao and Lo Lo. Villagers farm every scrap of soil, planting maize between the rocks, and weekly markets bring colourful traditional costumes. The nearest big town is Hà Giang, about twenty-six kilometres back, where you should fill the tank and check the bike.
The Ha Giang Loop is a famous adventure for riders, and this pass is one of its first great moments. The road is a ribbon of switchbacks cut into the mountainside, mostly paved but narrow, with blind curves, potholes, sudden fog and trucks and buses taking the middle of the road. Take it gently, use the horn at corners and watch for livestock. In the rainy season, from about May to September, landslides and slick surfaces are common, while autumn and spring offer clearer weather, though cold mornings.
Pack layers, a rain jacket and a spare phone battery, as it gets chilly at altitude. Buy water and snacks in town, and look for small roadside stalls selling sweet corn and tea. At the pass there are stalls and viewpoints, and a short stop gives you the best view of the Twin Mountains. Local guesthouses in Quản Bạ and Tam Sơn serve simple, tasty meals, and the Hmong market days make the village lively. Early starts help avoid cloud and traffic.