The Blue Mosque or Mosque of Sultan Ahmet I with seven minarets and the Fountain of Kaiser Wilhelm II, Constantinople. The capital city of the Roman Empire between 330-395 AD, in Byzantine times, Byzantium was considered the world centre of civilsation for 600 years. Then having been known under the name of Constantinople, after the declaration of the Republic in 1920s was renamed Istanbul. All business in Constantinople has historically been linked to the Bosphorus, dividing the European side of the city from the Asian side of the city. Istanbul is now the third largest city in the world with a population in excess of 11 million and the only metropolis in the world situated on two continents. Postcard by Publishing House of Rochat. Inspired to issue a series of cards of quite well-known views of Constantinople which they then washed out in various colours. This was perhaps, for Constantinople, an innovation and the cards proved to be very popular with the public.