Constantine the Great chose Byzantium as his new capital in the 4th century and renamed it as Constantinople. It remained the capital of the Eastern Roman Empire (395–1204 CE and 1261–1453 CE) for more than a thousand years. The city also served as the capital of the Latin Empire (1204–1261 CE) and later, of the Ottoman Empire (1453–1922 CE).
The city of Constantinople was a defensive shield for old Roman Empire's eastern provinces. Theodosius II (413-414 CE) built thick 18 meter tall walls to fortify the city. A chain of walls some 60 kilometers in length and ran across the Thracian peninsula strengthened the city's defense further. Many scholars believe that these fortifications contributed to the development the Eastern Empire, while the Western and Roman Empires collapsed.
Constantinople was the gateway to Christian Europe. However, in 1453 CE, the Ottoman Turks conquered the city after a long and harrowing siege under the leadership of Sultan Mohammed II.
C. A. & Co. was high-quality postcard publisher around the turn of the century, known for spectacular sunset views like those of Varanasi and Colombo (see links below).