Islam originated in the Arabian Peninsula in the 7th century AD. According to Islamic tradition, the prophet Muhammad began receiving revelations from God through the angel Gabriel around 570 AD. Muhammad shared his message with others in Mecca, but faced opposition from leaders there. He and his followers migrated to Medina, marking the beginning of the Islamic calendar. Islam then spread across Asia, Africa, and parts of Europe through military conquests and trade routes. Key cities in the early Islamic empire included Mecca, Medina, Damascus, and Baghdad.