This is the 17496th most frequent Turkish word.
i̇stanul
"Istanbul" in Turkish refers to the largest city in Turkey, formerly known as Constantinople.
Here, 'İstanbul' is used as a proper noun referring to the city of Istanbul.
İstanbul çok güzel bir şehir.
Istanbul is a very beautiful city.
In this sentence, 'İstanbul'da' (in Istanbul) is a locative form indicating the location.
İstanbul'da birçok tarihi yapı bulunur.
There are many historical structures in Istanbul.
Here, 'İstanbul'a' (to Istanbul) demonstrates the dative case used for expressing direction towards a place.