That's not mainstream nor the correct interpretation. Other hadiths of our prophet confirm that the second Constantinople is Rome. Thus both are capitals of the (Eastern and Western) Roman Empires. The Sultan who conquered Constantinople, Fatih Sultan Mehmet, sent the navy to Otranto/Italy and conquered there for this reason: to conquer the two Constantinoples and thus fulfill the prophecy. He died without doing it in accordance with the prophecies, the one to conquer 2nd Constantinople will be the Mahdi, expected leader of Muslims in the end times and his name will be the same as our prophet's: Muhammad ibni Abdullah (means son of Abdullah).