Unless you are a Shi’ite Muslim, the chances are that Mashhad will have passed under your radar. Lying in the northeast of Iran, Mashhad is the burial place of Imam Reza and, after Mecca and Medina, one of the most important pilgrimage sites in the Islamic world. The 9th century mosque is the largest in the world (by dimension, rather than capacity) and non-Muslims are welcome to explore the courtyards and prayer halls, as well as attend free lectures in English about the shrine’s history and the significance of Imam Reza.