 Hajj is one of the largest annual Muslim gatherings in the world, second only to pilgrimages to the mosques of Husayn ibn Ali and his half-brother Abbas in Karbala, Iraq, with attendance reaching 3 million in 2012.The Prophet's Mosque is located in Medina, making the city the second-holiest site in Islam, after Mecca.Medina is the final place-of-residence of Muhammad, and where his "qabr" (grave) is located.