Istanbul stands as one of Islam's most magnificent cities, featuring architectural masterpieces like the Blue Mosque, Süleymaniye Mosque, and the historic Hagia Sophia which served as a mosque for centuries. As the former capital of the Ottoman Empire, the city holds immense Islamic significance and was the seat of the Caliphate for over 400 years, making it a center of Islamic civilization and governance. Today, Istanbul's vibrant Muslim community of over 15 million people maintains rich Islamic traditions, with hundreds of active mosques, Islamic educational institutions, and cultural centers that preserve and celebrate the city's profound Islamic heritage.