The grand tradition of Ottoman architecture, established in the 16th century, was derived from two main sources. One was the rather complex development of new architectural forms that occurred all over Anatolia, especially at Manisa, Iznik, Bursa, and Selçuk in the 14th and early 15th centuries. In addition to the usual mosques, mausoleums, and madrasahs, a number of buildings called tekke s were constructed to house dervishes (members of mystical fraternities) and other holy men who lived communally. The tekke (or zeviye) was often joined to a mosque or mausoleum. The entire complex was then called a külliye. All these buildings continued to develop the domed, central-plan structure, constructed by the Seljuqs in Anatolia. The other source of Ottoman architecture is Christian art. The Byzantine tradition, especially as embodied in Hagia Sophia, became a major source of inspiration. Byzantine influence appears in such features as stone and brick used together or in the use of pendentive dome construction. Also artistically influential were the contacts that the early Ottomans had with Italy. Thus, in several mosques at Bursa, Tur., there are stylistic parallels in the designs of the exterior facade and of windows, gates, and roofs to features found in Italian architecture. A distinctive feature of Ottoman architecture is that it drew from both Islamic and European artistic traditions and was, therefore, a part of both.
The apogee of Ottoman architecture was achieved in the great series of külliyes and mosques that still dominate the Istanbul skyline: the Fatih külliye (1463–70), the Bayezid Mosque (after 1491), the Selim Mosque (1522), the Sehzade külliye (1548), and the Süleyman külliye (after 1550). The Sehzade and Süleyman külliyes were built by Sinan, the greatest Ottoman architect, whose masterpiece is the Selim Mosque at Edirne, Tur. (1569–75). All of these buildings exhibit total clarity and logic in both plan and elevation; every part has been considered in relation to the whole, and each architectural element has acquired a hierarchic function in the total composition. Whatever is unnecessary has been eliminated. This simplicity of design in the late 15th and 16th centuries has often been attributed to the fact that Sinan and many Ottoman architects were first trained as military engineers. Everything in these buildings was subordinated to an imposing central dome. A sort of cascade of descending half domes, vaults, and ascending buttresses leads the eye up and down the building's exterior. Minarets, slender and numerous, frame the exterior composition, while the open space of the surrounding courts prevents the building from being swallowed by the surrounding city. These masterpieces of Ottoman architecture seem to be the final perfection of two great traditions: a stylistic and aesthetic tradition that had been indigenous to Istanbul since the construction of the Byzantine church of Hagia Sophia in the 6th century and the other Islamic tradition of domical construction dating to the 10th century.
While mosques and külliyes are the most characteristic monuments of Ottoman architecture, important secular buildings were also built: baths, caravansaries, and especially the huge palace complex of Topkapi Saray at Istanbul, in which 300 years of royal architecture are preserved in its elaborate pavilions, halls, and fountains.