Conquest of Istanbul Day is observed in Istanbul, Turkey, every May 29. This local celebration commemorates the fall of Constantinople, which occurred on May 29, 1453, marking a significant turning point in Turkish history. The city, originally founded as Byzantium by Greeks in 657 BC and later renamed Constantinople by Emperor Constantine the Great in 330 AD, was besieged by Ottoman forces led by Sultan Mehmed II. The conquest led to the relocation of the Ottoman Empire's capital from Edirne to Constantinople, although the name Istanbul was not officially adopted until the 1930s. The anniversary is celebrated with various events in Istanbul, reflecting on the historical significance of the conquest and the end of the Eastern Roman Empire.