Everybody has a city that let them in immediately. The interesting question is not whether it was mystical, but why the feeling is so specific and so hard to argue with.
The dull explanations, which are largely correct
Light. Density. Whether the built environment is at a scale your nervous system reads as safe. Whether people make eye contact. Whether you happen to look like everybody else, or interestingly unlike them. Whether you arrived rested, in June, with no obligations and enough money for lunch.
There is also the small matter of being on holiday, a state so unlike your actual life that it should probably be inadmissible as evidence. Nowhere has ever felt like home while you were also doing your job there.
The astrological account
In astrocartography the placements most associated with this are the Moon and the IC — the angle governing home, roots, and the private version of you. The claim is not that the city is special. It is that a place emphasising those parts of your chart tends to be described this way by the person whose chart it is, and quite differently by whoever is standing next to them.
Which is the part worth keeping. Two people walk the same street; one relaxes and one counts the hours. The actual proposition here is not that certain cities are magic — it is that the magic is not evenly distributed, and it is distributed by chart rather than by charm.
Why the feeling matters even if the theory does not
A body that relaxes somewhere is telling you something, usually before your reasoning has caught up. That deserves attention regardless of what you believe about the Moon.
The failure mode is treating forty minutes of relief as a mandate. The feeling is real data about how a place affects you and no data at all about rent, visas, or whether you will still know anybody there in March. Take it seriously. Do not take it as instructions.