I recently passed through Singapore and rested for a few hours in the airport transit hotel. It’s a useful facility which can give you something useful to do with a layover, i.e. sleep.
The rooms are in a little warren of corridors, all completely contained within the airport terminal. And the rooms look like a standard business hotel room, with a desk, a bathroom and (of course) a bed.
That’s not all. These internal rooms also have windows. They aren’t real – how could they be? Each room has a set of drawn curtains right where you would expect a window. If you look behind the curtain you find a blank wall.
Why do we feel the need for a window? One definitely makes the room more welcoming. And, because you would only to to those rooms for a sleep (if you’ve been for some other purpose please don’t tell me) the curtains add to a feeling of night time, regardless of local time or your body clock.