Blue Mosque, also known as the Sultan Ahmed Mosque, is an Ottoman-era historical imperial mosque located in Istanbul, Turkey. A functioning mosque, it also attracts large numbers of tourist visitors. It was constructed between 1609 and 1616 during the rule of Ahmed I. Its Külliye contains Ahmed's tomb, a madrasah and a hospice. Hand-painted blue tiles adorn the mosque’s interior walls, and at night the mosque is bathed in blue as lights frame the mosque’s five main domes, six minarets and eight secondary domes. It sits next to the Hagia Sophia, the principal mosque of Istanbul until the Blue Mosque's construction and another popular tourist site.
The Blue Mosque was included in the UNESCO World Heritage Site list in 1985 under the name of "Historic Areas of Istanbul".
The Sultan Ahmed Mosque has five main domes, six minarets, and eight secondary domes. The design is the culmination of two centuries of Ottoman mosque development. It incorporates many Byzantine elements of the neighboring Hagia Sophia with traditional Islamic architecture and is considered to be the last great mosque of the classical period.