The Ottoman Turks settled in western Anatolia first and later on after the conquest of Constantinople they became the leading power of the Mediterranean between 15th and 18th century.
They gave importance to urban life and this led to the emergence of imaret a name for the compounds of a mosque, a tomb, a soup kitchen, a public bath and a religious school(madrasa). Each Ottoman sultan commissioned an imaret on his name which expedited the progress of urban life and architecture. The Ottomans placed a dome over every significant buildings leading to an internal order to emphasise regime’s authority. They embellished cities with great domes and minarets placed on hilltops. The Byzantine church Hagia Sophia, later transferred to a mosque, turned into a governing source of influence on Ottoman architecture. Sinan, the chief architect, impressed from Hagia Sophia and Byzantine samples and established an Ottoman style.
The initial references of Ottoman architecture were originated from Anatolian region such as beehive domes of Seljuk’s, imitating the masonry of Armenian churches and Persian like arcades. As a very early mosque architecture of Ottomans Orhan Gazi Cami become a base for many others. It has a reverse-T shape plan overlooking to the central markets. On the front facade has pointed arches as often seen in Islamşc structures but the masonry mostly resembles Roman style of opus mixtum with varying bands of limestone and brick. Similar to all other mosques the mosque had a fountain for the use of religious needs in an octagonal form. The two central domes of the mosque dominated an axis inside through Mecca.
Green Mosque (Yeşil Cami) also had a reverse-T shaped plan. On the contrary to the details of Orhan Gazi Cami, the Green Mosque made through proportionally and symmetrical matched elements. Unlike many others of its kind one should pass through an entrance hall to access to prayers hall and second level separated from prayers hall and used by the sultan. It resembles the Byzantine protocol used by Umayyads as well.
Another mosque in the very first capital of Ottomans, Bursa, Ulu Cami was differing from previous ones as not having a reverse-T shape plan, but a hypostyle hall. each of its bays carried a dome later became an essential for Ottoman style of architecture not only for mosques, but madrasas, baths etc.