This structural group, which occupies a special place in the Ottoman mosques of the early period, first emerged in the Anatolian Turkish architecture in the Bursa region during the reign of Orhan Gazi (1326-62). Structures of this type are known under a variety of names-Bursa-type; dervish; winged; dervish cell; reverse-T plan; annexed; and hospice-and have occasioned disagreements among proponents of differing views based on the functional scheme that have reached polemical proportions. This is because of the inclusion of units in these structures, which are in part or in whole abstracted from the mosque itself and which represent projections on the west and east sides of the mass that are distinct from the mosque unit devoted to worship; between these spaces known as cloister cells (tabhane) and the mosque itself, there is the central hall (sofa), which serves as a circulation area on the axis of the mihrap-portal and possesses the character of an inner courtyard covered by a dome. One may evaluate these structures, which typically present an inverted-T form, as miniature complexes resolved within a single mass. The mosque unit itself featuring a mihrap and minber and whose floor is raised to the level of the central hall stands on the south side of the central hall, which is entered on the axis of the north wall, adjoined by a portico. The cloister cells, which in some examples constitutes an eywan adjacent to the central hall whose floor is raised and leads to the central hall and which in others is abstracted by walls from the central hall, apparently served to house members of the Akhi fraternal organization, who directed activities that dominated almost every aspect of Ottoman social life in the founding period. The fore-runners of the cloister cell/dervish lodge mosque in Turkish architecture in Anatolia are the dervish cloisters of the Seljuk period whose courtyards are covered by domes and include madrasas with eywans and which present the same design characteristics.
Inscriptions and documents commonly refer to these structures and other contemporary institutions set up by pious foundations as soup kitchens (imaret). Undoubtedly, it is no coincidence that the dervish tradition and its offshoot, the Akhi brotherhood, which became very powerful in the Ottoman lands, emerged during the reign of Orhan Gazi, who was himself a member of the Akhis. Not surprisingly, after the conquest of Istanbul when the Ottoman state adopted a relatively more centralized imperial identity and, concurrently; distanced itself from the local administrative tradition represented by the Akhis, this structural type lost its former importance and, by the mid-sixteenth century; had been entirely abandoned.
The fırst significant execution of the cloister cell/dervish lodge mosque was the Orhan mosque in Bursa dated 1339-40. This structure though is rather early and represents a mosque type that would be rejected in the era of the classical style, bears certain basic characteristics that are trademarks of the Ottoman architecture. Hence, we see, for example, function given preferential weight in the design; moderate use of decoration on the interior of the spatial unit and the facade; interior design that can be easily perceived on the exterior of the units, through unity with the independent superstructure; and the interjection of movement in the mass. In the structure built of alternating courses of stone, the domes and cloistered vaults of the portico of five units are carried by pointed arches that rest on piers of dressed stone. The side facades in this arcade of the first monumental portico of Ottoman architecture (and, at the same time, the Turkish architecture of Anatolia) were not left blank; they were opened to the exterior by two pointed arches each, which spring from re-used composite capitals. These double arches, embraced by a large pointed arch, are in a gothic style, whose origins are Eastern and which spread through a vast geography that extends from Venice to the lands of the Mamlukes and the Crusader states of the Eastern Mediterranean. Incidentally; it is the first manifestation in the Ottoman architecture of a facade style that had also left its imprint on Byzantine structures. The surface area between the large arch and the twin arches is filled with a diamond-shaped section of brick and stone; in addition, round brick medallions whose counterparts are encountered in the late Byzantine architecture were placed between the arches on the north facade.
Both the central hall on a square plan, the mosque itself and the cloister cell units on rectangular plan that open on to the central hall by broad pointed arches, are covered by domes; the domes, which rise over octagonal drums, were assigned different heights. Triangular pendentives in the Seljuk style were used in the corner angles of the central-hall dome, which is the tallest of them all; prismatic triangles appear between the apertures on the drum. The squinches of the mosque dome are filled with large-scale prismatic triangles. The stucco mihrap bears unique and original ornamentation in the form of a stalactite cornice and a band with a geometric pattern; arid the triangular surfaces adjoining the intrados filed with stalactites have been enriched by stylized leaf motifs (Rûmi) in relief. The upper edges of the carrying walls on all the facades and the dome drums are finished by a zigzag pattern in brick. Shallow niches with pointed arches-whose widths and heights vary and some of which are decorated with zigzag imposts and round brick medallions-bestow a dynamic appearance on the side and rear facades. The Hüdavendigâr mosque and madrasa built during the reign of Murad I shortly after 1364-65 represents one of the most interesting experiments in Ottoman architecture in the formation stage. In addition to the unusual appearance of the mass and entrance facade, the curious two-storey design unites the scheme of a doister cell/dervish lodge mosque with that of an enclosed courtyard madrasa. The two-storey portal facade, which recalls that of a palace, is composed of two five-unit arcades, one above the other; the lower arcade is occupied by the portico, and the upper one belongs to the madrasa. This veranda, which may be classified as a kind of open central hall (hayat), commands a view of the Bursa plain. With the exclusion of the piers, the remaining facades of the structure are of alternating courses of stone and brick. The pointed arches that support the portico units covered by domes with pendentives are seated on piers of cut stone. Cloistered vaults cover both the open central hall belonging to the madrasa and the units on either side while the dome was preferred for the other units.
The central hall units open to the exterior with double pointed arches, each placed within a pointed arch; the geometric filling of brick and stone above the double arches of the side facades and an inverse-T pediment, which boasts the same kind of decoration are worthy of note. Columns stand in the center of the twin arches and brick piers stand between them which are very seldom encountered in the Ottoman architecture.
As a result, thanks to this effective arrangement of gothic and late Byzantine whose earliest execution is witnessed in the Orhan mosque in Bursa, an extremely lively appearance has been obtained on the portal facade of the Hüdavendigâr mosque and madrasa. By contrast, the side and rear facades are carrying walls that rise straight up with no gradation whatsoever with its windows few in number and small in size convey a static and massive expression The interior spaces of the building are dimly illuminated, which is also contrary to Ottoman architectural characteristic. Evidently, dissatisfaction with this state of affairs eventually led (probably in the seventeenth or eighteenth century) to the piercing of the lower portion of the wall by large rectangular windows. Moreover a stringcourse of small round arches, which starts at the portal facade and which increases in size at the conclusion of the outer hall of the madrasa, adds a kind of chateau-esque air to the mass. The same course motif is employed at the eaves of the dome of the central hall. The body of the cylindrical minaret of brick that rises from the carrying walls and the northeast corner of the structure are decorated with geometric bands.
Passing through the two units with barrel vault vaults that succeed the portal, one reaches the central hall. The central hall spatial unit on a square plan has two storeys and opens upon the upper portion of the central hall by six windows with round arches in the corridor that extends in front of the cells of the madrasa on the upper floor. These windows, which secured a visual link between the mosque and the madrasa and which necessitated its interpretation as a kind of closed-courtyard madrasa on the upper floor, were closed off bricked up in a modern renovation; thus, one of the most important architectural elements of the structure was destroyed. The dome of the central hall, whose peak was left open, rests on a drum that is square on the exterior and twelve sided on the interior. Triangular pendentives were used in the transition from the square base to the twelve-sided drum. Two cloister cells each are arranged on the east and west sides of the central hall; one is in eywan form opening onto the central hall, and the other is abstracted from this and covered by a barrel vault. The floors of both the cloister cells in the form of eywans and the main mosque unit oriented south are raised. The mihrap niche in the mosque on a rectangular plan with barrel vault stands behind a large niche with barrel vault. On the inside of the structure, the only unique structural element that has survived to the present are the small columns in the corners with capitals shaped in a diamond-shaped geometric pattern, the stalactite intrados of the mihrap. The painted decoration on plaster visible on the mihrap, the walls and the superstructure dates to the nineteenth century.
On the main floor two symmetrical staircases that ascend from the units behind the portal lead to the madrasa storey above. The school cells, rectangular in plan and barrel vaulted, are each illuminated by a small window. The corridor with pointed barrel vault onto which their doors open is in three sections, running along three sides (north, east, and west) of the central hall in a U-shape. An extension of this corridor presents a problematic in this structure; leading to the walls of the mosque unit, it continues as a narrow passage that is lit by tiny apertures like loopholes until it reaches a cell that occupies the space above the projection of the mihrap and whose function is unknown. The experimental combination of a two-storey mosque and madrasa in the Hüdavendigâr mosque and madrasa is apparently the first and the last example, for which no demand occurs in the later Ottoman architecture; however, this design treatment of partitioning a massive block into three in the interior was continued in the Yıldırım and Yeşil mosques, though no madrasa was housed on the upper floor.
The Yıldırım mosque which derives from the fourteenth century in Bursa and has given its name to the neighborhood, and the Yeşil mosque in İznik, were completed in the same year (1391). They are the first works in the early period of the Ottoman architecture in which were used unique solutions produced by the pre-Ottoman Turkish architecture in Anatolia, such as the replacement of alternating courses of stone and brick by carefully dressed stone and elimination of details of Byzantine origin and the re-used architectural elements. Nearly square in plan and of five domed units, the portico is preceded by an arcade of Bursa arches. Notably, on the lateral facade of the arcade, which is the most successful portion of the structure with its monumental dimensions and balanced proportion, are displayed twin Bursa arches inserted into a rectangular frame-an arrangement that was first seen in the Orhan mosque in Bursa. On either flank of the eywan with Bursa arches and dome, which contains the main door with compressed arch, is a side entrance, each with a stalactite niche and Bursa arch. Both these and the small stalactite mihrabs on the facade of the portico are crowned by windows belonging to units that are identified as raised platforms with balustrade for the private worship of the sultan, which constitute a partial upper floor in the north wing of the structure.
The central hall and the main mosque were designed on the square plan with dome, with the central hall’s dome ornamented by squinches and the other dome by a band of prismatic triangles. An eywan of Bursa arch and dome were designed on their sides; those on the north and the south are enclosed by walls and a row of three cloister cells covered by a cloistered vault are arranged. The south walls of the cloister cells on the south side are, in their entirety, covered with stalactite niches made of stucco with multifoil arches. In the middle of the wall, a great stalactite niche has been placed that appears to be a kind of air vent; though it resembles a fireplace, it has neither a chimney nor a hood. The rectangular and triangular shaped surfaces between these elements are filled with molded panels of geometric decoration. These stucco elements are of great value for the light they shed on similar examples encountered in secular structures in later periods; early examples from Ottoman secular architecture in the early period have been lost. Other unique decorative elements in the structure include are the triangles in the frame of the windows on the north facade with which it concludes; the series of cartoons filled with Arabic calligraphic inscriptions and the stalactite cornices of the windows on the lateral facades; and, in addition, the cartoon frame and the mihrap with stalactite intrados and hourglass columns.
Among the early works of the Ottoman architecture, the Yeşil mosque erected in Bursa by Çelebi Sultan Mehmed in 1419 is unquestionably the most discussed work-almost always in positive terms-and that is the reason of the attention brought by travelers and literary writers as well as native and foreign researchers. The Yeşil mosque owes its renown to the concentration, in the interior, of glazed tile decoration of high quality, rather than to its mass and facades. The harmony between the natural environment and these tiles, which recreate an eternal spring in the sanctuary of the mosque, must have served as inspiration for this couplet from the poem by A.H. Tanpınar titled “Time in Bursa”: “The green of the plain, the blue of the heavens/And the most divine of architectures.”
With the exclusion of the incomplete (or the uncompleted) portico and the small eywans on the north side of the central hall, the Yeşil mosque, which shares the general characteristics of the cloister cell/dervish lodge mosque, roughly repeats the design of the Yıldırım mosque. The walls are faced with courses of white marble blocks, and the row of windows arranged along the lower portions of the facades and the portal on the axis of the north facade are enriched by very showy stone ornamentation, some of which suggests the influence of Timurid art. The portal facade with the upper row of windows in a geometric network under Bursa arches, which belong to the raised platform with balustrade for private worship by the sultan are reminiscent of a palace facade. Construction of the arcade of the portico was abandoned-as it is evident by the existence of transitional elements at the arches on the wall-no doubt, so that the facade would not hide this beauty.
The Yeşil mosque is one of the rare structures in the history of the Ottoman architecture to possess a number of inscriptions identifying the artists. At the portal, the Arabic inscription in large Arabic letters (sülüs) placed between the compressed arch and the intrados furnishes the names of the founder (Çelebi Sultan Mehmed), the completion date (December 1419) and the architect (Ahî Bayezıd oğlu Hacı İvaz Paşa). The inscription located between the arch of the raised platform with balustrade for private worship by the sultan, which opens onto the central hall and the band of prismatic triangles of the last dome, indicates that the painted decoration (nakış) by İlyas Ali oğlu Ali was finished at the end of August 1424. The name of Muhammed Mecnün, the master tile maker is inscribed on the tile on the impost of the same arch. The collective signature of a group of artists from Azerbaijan-“the work of the masters of Tabriz” (“amel-i üstâdân-ı Tebriz”)-at the top of the hourglass column on the right side of the mihrap may also be noted.
On either side of the eywan succeeding the portal, which opens up by a Bursa arch onto the central hall, passages containing columns with re-used Byzantine capitals lead to the cloister cells at the northeast and the northwest corners. On the south side of these units, rectangular in plan and covered with a star vault, are in the form of a domed eywan and opened to the central hall by a pointed arch; on the opposite side of each cell is a second cell, domed and on the square plan, which is closed off from the central hall. The domes over the cloister cells on the south were designed as multi-foil and display painted decoration on plaster; the closed cloister cells possess stucco niches and vents resembling fireplaces like those in the Yıldırım mosque. On the north side of the central hall, whose dome is crowned by a lantern and which has an ablutions fountain in the middle area, opens to the main mosque by a broad Bursa arch with stalactite impost. The transition to the domes of the central hall and the mosque is provided by a band of prismatic triangles. On the north side of the central hall, adjacent to the entrance eywan, are eywans with Bursa arches and flat ceilings, which some scholars have interpreted as spaces reserved for the functionary who makes the call to prayer (müezzin) while others are of the opinion that they were reserved for state officials. The space above these eywans on the axis of the mihrap-portal is occupied by the raised platform with balustrade reserved for private worship by the sultan with Bursa arch, next to which are two units covered by a cloistered vault and dome with windows that open onto the central hall and the outside. These spatial units adjoining the raised platform with balustrade represent a solution to the problem of creating a kind of imperial pavilion within the body of the structure. The walls of the sanctuary, mihrab and the areas reserved for the sultan and the caller to prayer are faced with glazed tiles which exhibit mosaic tiles and colored glazed techniques. Besides the stucco and painted decoration in the closed cloister cells, the geometric and stylized vegetal (rumi) motifs on the wooden doors and windows shutters deserve mention. In addition, the silver inlay decoration on the iron window grill, a discovery of recent times, is the only known example of its kind.
The structural type represented by the Muradiye mosque dated from 1426 is the final important example of this structural type in Bursa. The design of the cloister cell/dervish lodge mosque, which was first observed in the Orhan mosque, now approximately one century later is met again in the Muradiye mosque. The Murad Hüdavendigâr mosque and madrasa present a design for a lively mass which had been interrupted and an elegant arcade at the portico. Similarly, alternating courses of stone and brick were preferred for the facades. The dome-covered five units of the portico on square plan with doistered vault rests on pointed arch piers and columns, which carry the upper structure. The surface area exclusive of the arches is decorated by a variety of non-repeating geometric patterns in brick and stone. The pointed relieving arches of the windows that open to the portico are decorated with mosaic glazed tiles; in addition the Bursa arch of the eywan containing the door with compressed arch is crested with the same kind of glazed tiles. In the structure whose interior divisions resemble those of the Orhan mosque, the walls of the central hall and mosque unit are covered with glazed tile panels that rise to a determined height.
Besides these mosques erected by the Ottoman sultans, the Demirtaş (Timurtaş) mosque, an example in Bursa from the Yıldırım Beyazıd reign, is remarkable for the unusual positioning of its minaret and its design. The free-standing minaret rises over six piers of laid brick that stand on a base of dressed stone; the hexagonal area below the base is occupied by an ablutions fountain.