
Iranian concept of 4 iwan in a mosque complex.
In 11th century Iran, hypostyle mosques started to be converted into four-iwan mosques, which, as the name indicates, incorporate four iwans in their architectural plan.
The Great Mosque of Isfahan reflects this broader development. The mosque began its life as a hypostyle mosque, but was modified by the Seljuqs of Iran after their conquest of the city of Isfahan in the 11th century.
Like a hypostyle mosque, the layout is arranged around a large open courtyard. However, in the four-iwan mosque, each wall of the courtyard is punctuated with a monumental vaulted hall, the iwan. This mosque type, which became widespread in the 12th century, has maintained its popularity to the present.