The greatest mosque in Istanbul was built between 1609 and 1616 by the architect Mehmet Agha, a student of the great Sinan. It was constructed on the orders of the 14th Ottoman Sultan, Ahmet I (reigned 1603-17). It is known as the Blue Mosque because of the mostly blue and green tiles which decorate the walls and domes. It is the only mosque in the Ottoman world with six minarets, which between them have a total of sixteen balconies