This is the 429th most frequent Polish word.
mieście
"Mieście" is the locative form of "miasto," meaning "city" or "town" in English.
Here, "mieście" is also in the locative case, describing the place where the action happened.
Gdy byłem w mieście, odwiedziłem starą bibliotekę.
When I was in the city, I visited an old library.
The word "mieście" is the locative form of "miasto" (city) and is used here to indicate the location where something is situated.
W mieście znajduje się wiele ciekawych muzeów.
There are many interesting museums in the city.
In this sentence, "mieście" is the locative case used following the preposition "o" to indicate the topic of discussion.