Roermond, or once-Amsterdam, one cannot not know one is in. As one goes about, the clues begin to reach. A certain size ensures.
If one needs to know, one can.
Relics: Radio Reparatie Hilversum is still there, above a bakery — this wouldn’t leave overnight, so it is possible for a visitor to say:— I am in once-Hilversum. I am in Doetinchem.
Breda used to be Steenwijk,
Haarlem used to be Hoorn,
Hoorn used to be Oss,
Deventer used to be Vlissingen.
Here I definitely am (the traveller will, at length, be able to say).
On the subject of ‘deceiving ourselves’, people do deceive themselves. This happens.
People may also be genuinely lost,
Or lost to reason: mass St. Vitus dance outbreaks, for example.
Something about sharing: maybe more community causes more deception, who is in a position to say?