(Reference: https://english.stackexchange.com/questions/124755/at-vs-in-followed-by-a-city-name) "The choice of in or at with a city depends on how speakers conceive that city in the context of the statement they are making. If the city is conceived as a two-dimensional place in which to live and work, then in is the usual preposition. If, on the other hand, the city is conceived as a single point rather than as a place with dimensions, then at is the common choice. This explains the difference between sentences such as: I live in Frankfurt. / The plane stops at Frankfurt on the way to Seoul. The meeting took place at Potsdam. / There was an explosion in Potsdam yesterday. On this basis, the expressions a hotel at Las Vegas and she was living at London are the idiosyncratic choices of individual speakers. I am not aware of any significant patterns of difference between BE and AE speakers." If you or anyone else wants help with grammar points such as these, feel free to book a trial lesson with me. :)

i dont know