The Sultan Ahmed Mosque (Turkish: Sultan Ahmet Camii) is a historic mosque in Istanbul. The mosque is popularly known as the Blue Mosque for the blue tiles adorning the walls of its interior. It was built from 1609 to 1616, during the rule of Ahmed I. Its Külliye contains a tomb of the founder, a madrasah and a hospice. The Sultan Ahmed Mosque is still popularly used as a mosque.
At its lower levels and at every pier, the interior of the mosque is lined with more than 20,000 handmade İznik style ceramic tiles, made at Iznik (the ancient Nicaea) in more than fifty different tulip designs. The tiles at lower levels are traditional in design, while at gallery level their design becomes flamboyant with representations of flowers, fruit and cypresses. The tiles were made under the supervision of the Iznik master. The price to be paid for each tile was fixed by the sultan's decree, while tile prices in general increased over time. As a result, the quality of the tiles used in the building decreased gradually.
The facade of the spacious forecourt was built in the same manner as the facade of the Süleymaniye Mosque, except for the addition of the turrets on the corner domes. The court is about as large as the mosque itself and is surrounded by a continuous vaulted arcade (revak). It has ablution facilities on both sides. The central hexagonal fountain is small relative to the courtyard. The monumental but narrow gateway to the courtyard stands out architecturally from the arcade. Its semi-dome has a fine stalactite structure, crowned by a small ribbed dome on a tall tholobate. Its historical elementary school (Sıbyan Mektebi) is used as "Mosque Information Center" which is adjacent to its outer wall on the Side of Hagia Sophia. This is where they provide visitors with a free orientational presentation on the Blue Mosque and Islam in general.