Constantinopolis ; Ottoman Turkish : Constantinople; Bulgarian : Цариград; 1410 and 1422 Mehmed the Conqueror entered Constantinople, and called it Islambol or Astana . The city became the capital of the Ottoman Sultanate . In 1930, it was renamed Istanbul as part of Ataturk's national reforms . The city was founded in 658 BC . It was once a fishermen's village and was known as Byzantium . In 335 AD, Emperor Constantine I made it the capital of the Eastern Roman Empire ( Byzantine Empire ) and became called Constantinople after Emperor Constantine I, the founder of the Empire. The city became the center of Eastern Christianity and a world cultural center, becoming the greatest city in the world at that time.

From its founding in the 4th to early 13th centuries , Constantinople was the largest and richest city in Europe ,  and was instrumental in the rise of Christianity during the Roman and Byzantine times, as well as being the center and seat of the Ecumenical Patriarch of Constantinople . The city also contained some of the holiest monuments in the Christian world such as the crown of thorns and the real cross .

During the golden age of the Byzantine Empire, especially under the rule of the Macedonian family, where their era was called the Macedonian Renaissance and the Cominians. During their reign, the Byzantine Empire witnessed a cultural and scientific renaissance. Constantinople was the leading city in the Christian world in terms of size, wealth and culture.After the loss of the greater number of provinces in the early 15th century , Eastern Roman (Byzantine) became a mere city that included the city of Constantinople and its environs, along with Maurya in Greece , and the city was eventually conquered by the Ottomans after a month-long siege in 1453. .

Constantinople was famous for its huge and complex defenses. Though the city was besieged on numerous occasions by various peoples, Constantinople's defenses proved to be at risk for nearly nine hundred years before the city was occupied by the Crusader forces in 1204 during the Fourth Crusade , becoming the capital of the Latin Empire . The city was recaptured again in 1261 by the Byzantine Emperor Mikhail VIII Palaeolog , and was conquered for the second and last time in 1453 when it was conquered by Ottoman Sultan Mehmed II .

Constantinople was famous for its huge and complex defenses. Though the city was besieged on numerous occasions by various peoples, Constantinople's defenses proved to be at risk for nearly nine hundred years before the city was occupied by the Crusader forces in 1204 during the Fourth Crusade , becoming the capital of the Latin Empire . The city was recaptured again in 1261 by the Byzantine Emperor Mikhail VIII Palaeolog , and was conquered for the second and last time in 1453 when it was conquered by Ottoman Sultan Mehmed II .

The city was also famous for its architectural masterpieces, such as the Eastern Orthodox Hagia Sophia , which served as the seat of the Ecumenical Patriarchate of Constantinople , along with the Holy Imperial Palace where the emperors lived, the Tower of Galata , the Hippodrome , the Golden Gate , as well as the rich aristocratic palaces, plazas and luxurious baths . Like the baths of Zakbikos . Constantinople had many artistic and literary treasures before falling in 1204 and 1453 . The city was also famous for its libraries, most notably the library of Constantinople , the last large library in the ancient world . The Library of Constantinople has preserved the ancient knowledge of Greece and the Greeks for over a thousand years and contained about 100,000 texts.  The University of Constantinople , founded by Emperor Theodosius II, is the first university in the world .  The university included colleges and schools in medicine , philosophy , theology and law , and various economic schools, colleges, art institutes, libraries, and fine arts academies were also open in the city.

Constantinople did not recover from the devastation of the Fourth Crusade and decades of misrule by the Latins, although the city partially recovered in the early years after restoration under the Palaeologian dynasty, the emergence of the Ottomans led to the Empire losing most of its territory. After the fall of the city at the hands of the Ottomans , Sultan Mehmed II transferred his capital from Edirne to Constantinople, and was named «Islambül» «Takht Islam»,  The fall of Constantinople led to the departure of a large number of scientists and philosophers of the city, from Rome and others, to the States The emirates and neighboring European kingdoms, before and after the siege of their capital, were dismantled, most of them landed in Italy, where they played a role in the revival of the different sciences and knowledge there, making the country the leader of the European Renaissance