Photos: Eid al-Ghadir celebrated at Imam Ridha Center of Peterborough, England

The Event of Ghadir (Arabic: واقعة الغدير), according to Shi'a beliefs, is among the most important events in the history of Islam, in which on his return from Hajjat al-Wida', the Prophet (s) introduced Imam Ali (a) as his vicegerent and people's guardian after himself at a place called Ghadir Khum, where everyone including greatest companions pledged their allegiance with Imam Ali (a).