Walk the Hoa Lu old quarter at night when the lanterns are up
The only after-dark walk here
Free
Free to walk, with charges for lanterns and rides. Go for the hoa dang lamp floating rather than the shopping, and treat it as the thing you do at 8pm after a day that started at 6am, not as a destination in itself. Busiest at Tet and on spring weekends, when Vietnamese families come in numbers regardless of the weather.