The Sundarbans are what happens when the Ganges, the Brahmaputra and the Meghna spread themselves out into the Bay of Bengal and the land simply gives up trying to be land. This is the largest mangrove forest in the world, shared between Bangladesh and India, and the part here lies in the south-west of Bangladesh, in the Khulna region, a maze of tidal channels, mud banks and islands that rise and fall with the tide. Nothing is solid for long, and there are no roads through the middle of it.
The forest takes its name, many say, from the sundari tree, whose roots send up little breathing spikes through the mud. It is the home of the Bengal tiger, which swims between islands and is said to be unusually willing to attack people, and the forest also shelters spotted deer, wild boar, saltwater crocodiles, river dolphins, and enormous numbers of birds, from kingfishers to herons. The sanctuaries here are a World Heritage site, and the trees have a practical job as well: they soak up storm surges, which is why villages behind the forest fared better in cyclones such as Sidr in 2007.
Riding here means riding to the edge. The roads on the Bangladeshi side run along flat, low-lying farmland, with shrimp ponds, rice paddies and tidal creeks, and traffic that is dense and unpredictable, a mix of buses, rickshaws, trucks, cattle and people. Surface quality changes from one village to the next, and ferry crossings are part of the journey, so allow far more time than the distance suggests. The dry season, from about November to February, is cooler and clearer, while the monsoon brings flooded roads and rough water.
Fuel and supplies are best found in the larger towns, Khulna and the port town of Mongla, before you head south, and from there the forest is explored by boat with a licensed guide and a permit from the forest department, not by bike. On the way, the old mosque city of Bagerhat is worth the detour. Its sixty-dome mosque, built in the fifteenth century under the governor Khan Jahan Ali, is the most remarkable building in the region.