<P> The "Gate of Felicity", the "Sublime Gate", and the "Sublime Porte" were literally places within the Ottoman Sultans' Topkapı Palace, and were used metonymically to refer to the authorities located there, and hence for the central Ottoman imperial administration . Modern historians also refer to government by these terms, similar to popular usage of Whitehall in Britain . The sublime Gate is not inside Topkapı palace; the administration building whose gate is named Bâb - ı Âlî is between Agia Sofia and Beyazit mosque, a huge building . </P> <P> Many peoples neighboring on the Byzantine Empire used names expressing concepts like "The Great City", "City of the Emperors", "Capital of the Romans" or similar . During the 10th to 12th century Constantinople was one of the largest two cities in the world, the other being Baghdad . </P> <P> The medieval Vikings, who had contacts with the Byzantine empire through their expansion through eastern Europe (Varangians) used the Old Norse name Miklagarðr (from mikill' big' and garðr' wall' or' stronghold'), later Miklagard and Micklegarth . This name lives on in the modern Icelandic name Mikligarður and Faroese Miklagarður . </P> <P> East and South Slavic languages referred to the city as Tsarigrad or Carigrad,' City of the Tsar (King)', from the Slavonic words tsar (' Caesar' or' King') and grad (' city'). Cyrillic: Царьград, Цариград . This was presumably a calque on a Greek phrase such as Βασιλέως Πόλις (Basileos Polis),' the city of the emperor (king)' . The term is still occasionally used in Bulgarian, whereas it has become archaic in Russian, and Macedonian . In Croatian, Serbian and Slovene, Carigrad is a living alternative name for the modern city, as well as being used when referring to the historic capital of the medieval Roman Empire or the Ottoman Empire . In Czech (a West Slavic language) this Slavic name is used in the form Cařihrad (used in the 19th century, now only occasionally). It was also borrowed from the Slavic languages into Romanian in the form Țarigrad, though Constantinopole remained the far more widely preferred term . </P>

When and why did constantinople change to istanbul