The Mosque of Fakhr al-Din, built by the first Sultan of Mogadishu in the thirteenth century, indicates formal architectural design. It is built in a compact rectangular plan with a strong, domed mihrab axis and a lofty prayer hall. Its use of conical vaults, the finely squared coral blocks of its construction, and the transitions of curved pendentives in place of squinches, further attest to the fine attention to detail and artistry at Fakhr ad-Din. The mosque, together with Husuni Kubwa on the island of Kilwa, are the two earliest remaining buildings on the East African coast and reveal planning more sophisticated than anything for centuries subsequent. Today Fakhr al-Din Mosque is located between the quarters of Xamar Weyn and Sheikh Muumin in the Somali capital city.
The entry façade has three doorways surrounded by slabs of paneled marble and carved coral with recessed orders and conical bosses jutting from their architraves. The central door of the three displays particularly ornate floral interlacing and carries an inscription. Upon entrance through these three doors, one arrives in one of three small ablution lobbies where there is a second set of doors. Again, the centermost of these doors is the most impressive. It is recessed via shallow stepped corbelling and is covered with marble slabs smothered in intertwined floral patterns. This door contains a diaper pattern of diamond shapes excised into the projecting coral bosses inset into the spandrels of the arch which is surmounted by a triple frieze.
These three ablution lobbies open into a narrow, transverse courtyard. In the southwestern corner of this court is a tiny barrel-vaulted room dating from the thirteenth century.
Beyond this courtyard is an arcaded portico approximately equal in area to the courtyard and spanning the face of the mosque. The portico is divided into five bays and the central bay is covered with a high, octagonal fluted dome on axis with the mihrab and the inner dome. This dome is reminiscent of an Anatolian conical type and is decorated with cusped plasterwork on the interior and exterior. The portico has remarkable elements such as curved column capitals quite rare on the east coast and only otherwise found at Kilwa. Two marble finials in the portico of the mosque have square shafts with diamond patterns carved into them. One passes from the portico through yet another choice of marble paneled doorways into the square prayer hall.
The prayer hall itself is remarkably spacious for an East African mosque. Only two polygonal columns interrupt the space and carry the longitudinal beams supporting the high ceiling. The internal division of space into nine bays is apparent only when looking up at the rafters above, as opposed to the more common East African layout of aisles dividing the space by columns which obscure a direct view of the mihrab. Secondary beams transect the corner bays creating an octagonal roof structure and a drum upon which the dome sits above the central bay. The shape of this "sugar-loaf" dome recalls Sudanese tombs and its style is dated to the original thirteenth century mosque. The exterior of the central dome was surmounted by a large Chinese celadon jar. Two side rooms run alongside the central prayer hall.
The alcove of the mihrab is inlaid with an Indian marble carving of a lamp hung by a chain from the apex of a cinquefoil arch that replicates the mihrab around it. Above this marble work is a glazed tile with an inscription of the year 1269, a religious verse, and an indecipherable name (perhaps the artist's or the architect's). The lamp motif, as well as the diamond carvings in the portico, also appear at Kilwa, suggesting that they may have been imported from elsewhere to both Mogadishu and Kilwa. The glazed tiles which depict mihrab arches and columns are, however, unique to Fakhr al-Din. The existing mihrab was probably built in the eighteenth century and is much plainer than that of the thirteenth century, although it incorporates remains from the earlier version. This newer version of the mihrab apse is a rectangular recess broken by a string course underneath an elliptical arch.