The mosque is situated in the southwest of Toon archaeological site.
Some researchers believe that this mosque was built during the Seljuk Dynasty in the 11th century; others, however, say it was constructed in the 7th century. The porch of the mosque is 16 meters high. The decorative brick of this porch repeats a geometric shape. There are also paintings on the stucco in the interior. The mosque has a large shabestan (prayer hall) with columns of two meters in diameter. Some 100 columns, which are as tall as 5.2 meters, hold the heavy ceiling of this shabestan.
Researcher and archeologist, Rajabali Labbaf-Khaniki, said the city of Ferdows was called Toon until 1936; and the Grand Mosque of Ferdows was called the Grand Mosque of Toon.
The researcher told ISNA that the city was a prosperous area from the 7th century until it was hit by a devastating earthquake in 1968. Labbaf-Khaniki added that famine, invasions and earthquakes damaged the city but failed to remove it from the map.
He said the architecture of Ferdows’s mosques, traditional bathrooms, cisterns known as ab anbars, which have remained from old times, are indicative of the significance and credibility of the city. The archeologist believes the Grand Mosque of Ferdows has a special status among the historical monuments of the city.
Labbaf-Khaniki said the Grand Mosque represents the grandeur of Toon (the former name of the city of Ferdows) before it was plundered and destroyed during the invasion of the Mongols in the 13th century.