What was the Istanbul called before the Ottomans conquered the city in the 15th century?

Before the Ottomans conquered the city in the 15th century, Istanbul was known as Constantinople. It was named after the Roman Emperor Constantine the Great, who refounded the city in 330 AD as the new capital of the Roman Empire. Constantinople was a significant cultural and political center, known for its strategic location and wealth. The city continued to hold great importance until its conquest by the Ottomans in 1453.