Çoban Mustafa Pasa Complex stands on a hill to the northwest of Gebze. Enveloped by roads on four sides, the buildings of the complex occupy a rough rectangular site that measures about hundred and twenty meters by hundred and ten meters. According to the inscription on the mosque's portal, the complex was commissioned in 1523 by Çoban Mustafa Pasa (d. 1529), who left his life as a shepherd (çoban) to join Selim I's (1512-1520) military campaign to Egypt, eventually becoming the Governor of Egypt and a vizier and son-in-law to the sultan.
Although the mosque complex is mentioned in court architect Sinan's Book of Buildings (Tezkiret-ül Bünyan), it was most probably built under the supervision of a former court architect, with Sinan involved as an assistant. Some other sources state that the complex was enlarged by Sinan in 1538.
The buildings are aligned with qibla on an axis slightly east of south. The mosque is placed at center, preceded by a rectangular forecourt centered on an ablution fountain. To its south is a large walled garden, enclosing the founder's tomb located behind the qibla wall. A continuous line of subsidiary structures envelop this core on three sides: a madrasa and dervish lodge to the east, a caravanserai with stables to the north, and a hospice and soup-kitchen to the west. Currently, the complex is primarily entered from the gate between the hospice and the soup-kitchen, although a grander, domed entry pavilion is located in axis with the mosque entrance, between two halls of the caravanserai. The dervish lodge and the madrasa are entered from their own courts with gates facing west and south, respectively.
The mosque of Çoban Mustafa Pasa is a single domed prayer hall entered from a five-bay portico to its north. Its square plan measures about twenty meters per side on the exterior, and the portico projects beyond it by two and a half meters on either side. The minaret with its single balcony is accessed from the western bay of the portico behind which it rises, attached to the western wall of the prayer hall. The domes of the portico rest on pendentives carried on pointed arches that rest on six marble columns with carved stalactite capitals. The central bay with the mosque entrance has a smaller but elevated ribbed dome. The portico façade is articulated with a window and a mihrab niche on each side of the portal.
Braced with buttresses on the exterior, the dome of the prayer hall rests on squinches on the inside, which transfer its load to two-meter-thick walls. Three tiers of windows illuminate the interior; eight casements on the first level, four arched windows at the mid level and four circular honeycomb windows at the top. There are eight additional windows pierced into the drum of the dome. The muezzin's platform (mahfil), which is accessed with a staircase embedded in the northern wall, is carried over five pillars.
In spite of its small size, the mosque of Çoban Mustafa Pasa is significant in its wealth of architectural ornamentation. The portico and the interior walls of the mosque are covered up to halfway with polychromatic marble plates, inscriptive panels and decorative bands in Mamluk style, carved by artisans from Egypt. The entrance to the minaret is framed with blue marbles, and topped by an arch with marble voissoirs of alternating colors. The interior of the dome is decorated with painted arabesques. Muqarnas carvings adorn the hoods of the portal and the mihrab niche, the minbar and the dome's squinches.
The prayer hall is built of alternating rows of brick and cut stone, with only cut stone used on the portico. The domes and the conical crown of the minaret are covered with lead on the exterior.
Tomb of Çoban Mustafa Pasa:
The tomb is a domed octagonal chamber, entered from the north through a single-bay portico facing the mosque's qibla wall. The slanted portico roof is carried on two pairs of marble pillars. The decorations of the tomb include the polychromatic tiling on the interior and stained glass windows.
Madrasa and Dervish Lodge:
The madrasa is located at the southeast corner of the complex and is entered from a court of comparable size to its south. Its rectangular plan centered on an inner courtyard is surrounded by an arcade on three sides giving access to twenty student cells. The large classroom occupies the eastern side of the courtyard and has a portico with slanting eaves. A doorway along the northern wing leads to the forecourt of the dervish lodge, where the toilets are also located. The dervish lodge is a rectangular building elongated on the north-south axis, containing domed cells centered on a narrow inner court. It is adjoined by a ceremonial room with two domes to its north.
Soup-kitchen, Hospice and Caravanserai:
The soup-kitchen is located to the west of the mosque and consists of domed cells lined up along the north-south axis. It contains the kitchens, a bakery and dining and storage rooms. The eight guest rooms of the hospice are located to the north of the soup-kitchen, each room accessed from an arcade facing the mosque forecourt. The caravanserai has halls on either side of the domed entry pavilion of the complex. Both halls are covered by two barrel vaults carried on four piers.
The Çoban Mustafa Pasa complex was deserted for many years prior to the launching of a nine-year restoration by the General Directorate of Religious Endowments in 1961 that was led by architect Cahide Tamer. Most of the buildings are well preserved today, with some of the subsidiary structures leased to non-profit organizations.
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