The Holy Shrine

First place every one should visit in Mashhad is the Holy Shrine.

The Imam Reza Shrine in Mashhad,Iran is a complex which contains the mausoleum of Imam Reza, the eight Imam of Twelver Shi'ities.
It is the largest mosque in the world by dimension and the second largest by capacity.Also contained within the complex are the Goharshad Mosque, a museum, a library, for seminaries, a cemetery, the Razavi University of Islamic Sciences, a dinning hall for pilgrims, vast prayer halls and other buildings.
The complex is the center of tourism in Iran, the Shrine itself covers an area of 267,0798 m2 while the seven courtyards which surround it, cover an area of  331,578m2 - totaling 598,657m2.