The Goharshad Mosque is the great Timurid prayer hall attached to the Imam Reza Shrine, completed in 1419 and one of the most accomplished Islamic buildings of its century. The mosque is built around a square courtyard with four iwans — the great south iwan, crowned with a turquoise dome, is the architectural climax — and the surfaces are covered in some of the finest 15th-century mosaic tilework anywhere.
The mosque is inside the shrine complex and visited as part of the same tour. The tilework deserves a slow look at close range, particularly the calligraphy bands and the inscription naming Goharshad herself as patron.