The Imam Reza shrine in Mashhad, Iran, is a complex which contains the mausoleum of Imam Reza, the eighth Imam of Twelver Shias. It is the largest mosque in the world by area. Also contained within the complex are the Goharshad Mosque, a museum, a library, four seminaries, a cemetery, the Razavi University of Islamic Sciences, a dining hall for pilgrims, vast prayer halls, and other buildings.

Imam Reza’s holy shrine is a complex of buildings formed progressively over almost a thousand years, around which the city of Mashhad was created according to the needs of this outstanding pilgrimage center. The relationship between the city and the holy shrine during different periods of time lead to a unique experience in the urban planning of the area, a practice which later transferred to the other pilgrimage cities by visitors, especially Shias.

The complex contains a total of seven courtyards, which cover an area of over 331,578 m2. The courtyards also contain a total of 14 minarets and 3 fountains.

The shrine itself covers an area of 267,079 square meters while the seven courtyards which surround it cover an area of 331,578 square meters, totaling 598,657 meters. Every year the ceremony of Dust Clearing is celebrated in the Imam Reza shrine.

According to wikipedia