Blue Mosque (İstanbul), Turkey, also known as Sultan Ahmet Mosque, one of the principal mosques of the city. It was built between 1609 and 1616 for Sultan Ahmet I by Mehmet Aga, a pupil of Sinan, considered the greatest architect of the early Ottoman Empire, and is known as the Blue Mosque on account of the predominantly blue and green tilework and painted decoration of its interior.

The mosque is surrounded by an openwork wall, and its courtyard is formed by arcades topped with domes. The courtyard has monumental gateways on three sides and a slender tower, or minaret, at each of its two outer corners. The mosque itself is modeled after two other great religious buildings of İstanbul: Hagia Sophia (Church of the Holy Wisdom), built between 523 and 527, and considered the greatest building of the Byzantine Empire (see Byzantine Art and Architecture); and the Süleymaniye Mosque, which was designed by Sinan. The basic design of all three structures is the same: an almost square space surmounted by a dome. The dome of the Blue Mosque is flanked on four sides by half-domes, and surrounded by a further arrangement of turrets, domes, and half-domes. Four minarets rise from the corners of the mosque.

The painted decorations on the domes and upper sections of the mosque are modern imitations of 16th- and 17th-century designs. The lower walls, however, are covered with original tiles from the nearby town of Iznik, well-known in the 16th and 17th centuries for this type of work. The tiles are painted with roses, carnations, tulips, lilies, and other plant motifs in subdued shades of blue and green. The floral and geometrical arabesques painted on the wooden ceiling under the sultan's lodge are also original. Other notable features include the doors and shutters, made of wood inlaid with ivory, shell, and mother-of-pearl; the marble mimbar, a stepped platform used for preaching; and the mihrab, a niche that indicates the direction of the Muslim holy city of Mecca. In the mihrab is a stone from the Kaaba, the central shrine of Islam in Mecca.