Sultan Ahmet Mosque or the so called Blue Mosque is one of the most outstanding works of the 17th century in the style of the Architect Great Sinan. It was architected by Sedefkar Mehmet Ağa who was the successor of Sinan. It was built by the Ottoman sultan Ahmet I between 1609 and 1616 in the Historical Peninsula. The mosque is lined with İznik (Nicaea) style ceramic tiles in white, green and blue colours and the interior ornaments of the main dome and the secondary domes are hand-drawn in blue colour. Therefore the mosque is called as Blue Mosque by the Europeans. After the Hagia Sophia was converted to a museum in 1934, it became the principal mosque of Istanbul. More than 200 stained glass windows admit natural light. The great tablets on the walls are inscribed by calligrapher Seyyid Kasim Gubari of Diyarbakır. It is a complex with the surrounding buildings and the first mosque with six minarets.