The Blue Mosque of Istanbul, also known by its official name, Sultan Ahmet Camii (Turkish: Sultan Ahmet Camii), is a historic mosque in the Ottoman Empire located in Istanbul, Turkey. It was built between 1609 and 1617, during the reign of Ahmed I, and is still a functioning mosque today. It also attracts a large number of tourists and is one of the most iconic and popular monuments of Ottoman architecture. The mosque has a classic Ottoman layout, with a central dome surrounded by four half-domes in the prayer hall. In front of it is a large courtyard flanked by six minarets. Inside, it is decorated with thousands of Iznik tiles and features a predominantly blue floral pattern, which gave the mosque its popular name. The mosque's külliye (religious complex) includes Ahmed's tomb, an Islamic madrasa, and several other buildings in various preserved states. The mosque was built next to the former Hippodrome, opposite Hagia Sophia, another popular tourist attraction. The Blue Mosque was included in the UNESCO World Heritage List in 1985 under the name "Historic District of Istanbul".