Jamkaran, Iran (on the outskirts of Qom) is the site of the Jamkaran Mosque, a popular pilgrimage site for Shi'ite Muslims. Local belief has it that the Twelfth Imam (Muhammad al-Mahdi) — a messiah figure Shia believe will lead the world to an era of universal peace — once appeared and offered prayers at Jamkaran. On Tuesday evenings especially large crowds of tens of thousands gather at Jamkaran to pray and to drop a note to the Imam in a well at the site, asking for help with some problem.

en.wikipedia.org/wiki/Jamkaran