Door and what it replaces
Door: hotel morning pickup in Hanoi, or board at Giap Bat / a long-distance station (per operator). One-way is roughly 2.5–4 hours depending on traffic — it consumes the whole day. Use it to replace West Lake day or south day, not “Hoan Kiem morning + Halong afternoon.” Islands stay off this station’s city place graph.
The night you return
Return night: ban Beer Street, Train Street and a forced puppet show — after boat motion and the ride, one hotel-area meal or an early West Lake sleep only. If Ba Dinh is tomorrow, keep the mausoleum for morning and do not stay out late. Overnight cruises: do not jam city night lanes on the way back either.