There is a small rectangular mosque attached to the western part of the burial chamber. It is famous as Masjid-e- Bala-e- Sar-e- Mubarak-e- Hazrat because the pilgrims enter this mosque from western side of the Holy Imam's burial chamber which is called Bala-e-Sar of the Holy Imam (A.S.). This sacred mosque has a history of over ten centuries. It is one of the oldest existing mosques in Mashhad, and was built by Abul Hassan Dabir during the reign of Sultan Mahmud of Ghazni (998-1020 A.D.). Ibn Batuta who visited Mashhad in 734 A.H/1333 A.D. has mentioned this mosque in his travel account. The length of the mosque is 8 meters, breadth 5 meters and height 10 meters. The walls are
covered with marble upto 90 centimeters, the next 1.70 meters with expensive Sultan Sanjari glazed tiles and the rest of the wall and ceiling is covered with beautiful mirrors. There is a mihrab connected to the holy burial chamber and the walls around the mosque are inscribed with Quranic verses in Thulth script.
This mosque has three terraces in the east, west and north. Its eastern terrace is adjacent to the Holy Shrine. Its western terrace is attached to the Dar-al Siyadah porch through a silver window. And the northern terrace of the mosque is attached to the Dar-al Shukr porch.