On a narrow lane running roughly parallel to and west of Hanoi's central railway station, residents have built their lives around the tracks. The alley is perhaps two meters wide, and the train — a working service, not a tourist attraction — passes twice a day in each direction, its wheels a few centimetres from the facades of houses, cafes, and shops. When a train is due, residents pull in their chairs, fold away their tables, and stand in doorways as carriages grind past at walking pace.
The cafes that have opened along the alley are now the primary reason visitors come, and the city has at various points tried to regulate or shut them down on safety grounds. Check locally before you go, as access has fluctuated. When it's open, arrive thirty minutes before the scheduled train time (roughly 3:30pm and 7:30pm, though schedules vary — confirm before visiting) and position yourself along the safer sections, where locals sit. The train is genuinely impressive at close range. It's not a managed tourist experience; it's just a railway that people happen to live next to, which is what makes it worth seeing.