The Friday mosque of Gunabad is located in the south of Khorasan province. A valuable building from the Kharizmshahid dynasty (ca. 1075-1230), it was damaged by earthquakes and renovated several times. A major renovation was undertaken in the Qajar period (1779-1924).
The mosque is a two-iwan mosque centered on a large courtyard, forty-four by sixty-six meters. It is oriented north-south, with two main entrances at the northeast and southeast corners of the mosque. The northeast entrance leads through a corridor to the courtyard. The main courtyard iwan, which contains the mihrab, is along the south (qibla) wall of the courtyard; a square prayer hall adjoins this south iwan, which is nine meters wide, eighteen meters deep, and twenty meters high. A smaller iwan, also joined to a prayer hall, runs along the north side of the court; this iwan is six and a half meters wide, eleven meters deep, and twelve meters high. The remains of two minarets, probably destroyed in an earthquake, rest atop the iwan walls. The prayer hall adjoining the east corner of the north iwan measures eleven and a half meters by seventeen meters. Its roof is supported by its walls and an additional four columns that are square in plan.
An prayer hall with seven arcades runs along the east side of the court. Square in plan and measuring ten by ten meters, the east prayer hall is roofed by a dome that is supported by four columns located at each corner of the hall. Along the west is an arcade divided into seven sections and topped with small domes.
The mosque is constructed of brick, and its interior is stuccoed. Its northeast entrance has a (probably Qajar-period) portal featuring a pointed arch with floral patterns carved in stucco. The south iwan is decorated with brick ornament and polychrome tiles, and its interior is adorned with Kufic arabesques and a muqarnas ceiling. The north iwan is also ornamented with brick and tile work. Its interior walls are decorated with carved stucco up to a height of six meters.
The stucco mihrab is half-octagonal in plan and is decorated with geometric and floral patterns as well as Kufic inscriptions. The remains of an older stucco mihrab with geometric patters were found on the qibla wall of the eastern prayer hall. The arcades facing the courtyard are closed with wooden doors shaped like pointed arches. Under the arch of the portal leading into the main prayer hall is a Kufic inscription in brick dating from the Seljuk period; this inscription was later covered.