Constantinople(Name of present-day Istanbul from 330-1930 C.E.. Previously known as Byzantium) proper noun [UK: ˌkɑːn.stæn.təˈno.pəl] [US: ˌkɑːn.stæn.təˈno.pəl]
Istanbul(largest city of Turkey and last capital of Ottoman Empire) proper noun [UK: ˌɪ.stæn.ˈbʊl] [US: ˌɪstan.ˈbuːl]