Visitors notice it on the first evening. Walk along any residential canal after dark and you look straight into people's front rooms, lamps on, curtains open, somebody reading on a sofa three metres from the pavement. It is a local habit, and it tends to prompt a sensible question once the guest is back in a hotel room with a massage booked: can anyone see into my hotel room, and should I do anything about it? The answer depends on the building, and checking takes about two minutes.
How Amsterdam windows actually work at night
A lit room with a dark street outside is a stage. From the inside, the glass turns into a mirror and you see your own reflection, which gives the false impression that the window is opaque. From the outside, everything in the room is visible in detail. The effect is strongest with the ceiling light on and weakest with one low lamp at the far side of the room, but even a single lamp is enough to show a figure to someone standing on the other side of a canal. That is one more argument for the single low lamp over the overhead fitting, though it is not a substitute for a curtain.
So the real question is not whether the window faces anything important. It is whether anyone can stand somewhere with a line of sight to it, and in the centre the honest answer is usually yes.
The rooms to think about
Canal-facing rooms in the older hotels look across water that is often only twenty metres wide at the houses opposite, many of which are homes with the local attitude to curtains. Ground-floor and half-basement rooms sit at pavement height, where passers-by are closer than anyone inside expects, and on the canals the tour boats in summer run past at eye level with windows until late. Rooms on narrow side streets can be overlooked by windows barely a street's width away.
At the other end are the rooms nobody needs to think about: courtyard-facing rooms in the canal hotels, which are the quietest and least overlooked in the centre, and high floors in the business towers, where the nearest window at the same height may be half a kilometre off. The Centrum hotel guide describes the building types, and it is worth reading if you have a choice of room.
Can anyone see into my hotel room? The two-minute test
Turn on the light you plan to use during the session, usually the bedside lamp, and turn everything else off. Close whatever curtains the room has. Then go and look at the edges. Light leaking round the sides of a curtain means a line of sight into the room, and a strip of street visible through the gap from inside means the reverse is also true. A curtain that glows evenly with the lamp behind it is a sheer, and sheers show silhouettes clearly from outside even when they look solid from within.
What you want is a heavy layer drawn all the way across, with the edges tucked or overlapping. Most hotel rooms have two curtain layers, a sheer and a blackout, and the blackout is the one that matters here. If the room has only sheers, which happens in a few design-led hotels, keep the lamp on the side of the bed away from the window, and ask the desk whether the room has blinds you have missed; they are often hidden in the window recess.
Mirror glass and the towers
The glass towers in the business district have a trick of their own. Reflective glass works as a one-way mirror in daylight, when the outside is brighter than the inside, and reverses completely at night. A room that felt entirely private at four in the afternoon is fully visible from the next tower at ten. The blinds in those rooms are there for this reason, and they should be down before the evening starts.
Skylights, doors and the rest
Attic rooms under the roof often have a skylight rather than a window, and skylights are seldom overlooked unless a taller building stands next door. Rooms with glass doors onto a balcony or a small terrace need the same curtain check as any window. And a room door with a gap underneath it lets light and sound into the corridor, but nobody sees anything through it, so it can be ignored.
Why this matters more for a session
It matters for the obvious reason, but also for a practical one: you will relax faster in a room that you know is private. A guest who keeps glancing at the window is not lying still, and an hour spent half-aware of the street is a lesser hour, when the whole idea of an in-room massage is that the room belongs to you. The discreet booking guide covers the arrival side of privacy; the window is the part only you can check, and it is best done before the confirmation arrives rather than after the knock.
Therapists check it too, in passing, and will draw a curtain properly if you have missed a gap. But two minutes spent on it beforehand means the first thing she does in the room is start, not adjust.