Jamkaran, Iran (on the outskirts of Qom) is the site of the Jamkaran Mosque, a popular pilgrimage site for Shi'ite Muslims. The pilgrims come especially to drop a message into a holy well, which they hope will be received by the Imam Mahdi. Most pious Shia Moslems do not seriously imagine that the Imam Mahdi is sitting at the bottom of the well reading those notes. But there is a significant body of writing that the Imam Mahdi is hidden but active in the world helping those who are needy.
Sheikh Hassan ibn Muthlih Jamkarani recorded encountering the Imam Mahdi in 373 A.H. (974 AD) near a well where the Jamkaran Mosque is now located. The Imam Mahdi was also accompanied by Al-Khidr.[1] The 12th or Hidden Imam is expected to rise from the Jamkaran well revealing himself and signaling completion of the age. This is similar to how Christians anticipate the second coming of the Christ except that one specific place is named as the arrival point.
One of the first acts of the government of President Mahmoud Ahmadinejad was to donate £10 million to the mosque.[2]
Jamkaran Mosque, irib.ir
This Mosqe is significant becase of the wide spread belief that the hidden Imam, the 12th Imam, Zaman will reappear from Jamkaran well at the appointed time. The Jamkaran Mosque is the Mosque at that well.
http://www.persiancarpetguide.com/sw-asia/Rugs/Persian/Qum/Jamkaran_Mosque_of_Qum.htm
Jamkaran Mosque, irib.ir