This is the 7509th most frequent Turkish word.
güzelhisar
"Beautiful fortress" or "lovely castle."
Here, 'Güzelhisar' is used as a proper noun to refer to a specific place.
Bugün arkadaşlarımla Güzelhisar'a gittik.
Today, we went to Güzelhisar with my friends.
In this case, 'güzelhisar' is used as a common noun, meaning 'beautiful castle'.
O eski güzelhisar, şimdi turistik bir mekan olmuş.
That old beautiful castle has now become a tourist spot.
Here, 'Güzelhisar' is again used as a proper noun, and its meaning is emphasized by the description in the sentence.