This is the 4299th most frequent Turkish word.
sivas
Sivas: A city in central Turkey.
In this sentence, 'Sivas' is used as the name of a city, a proper noun.
Sivas Türkiye'nin güzel bir şehridir.
Sivas is a beautiful city in Turkey.
Here, 'Sivas' modifies 'kangalları', referring to the dogs originating from Sivas.
Sivas kangalları çok ünlüdür.
Sivas' kangal dogs are very famous.
In this usage, 'Sivas' is combined with the preposition 'to' (as 'Sivas'a'), indicating motion towards that place.