Medina, originally Yathrib, is the city to which the Prophet Muhammad migrated in 622 CE — the Hijra that marks the start of the Islamic calendar — and where the first Muslim polity was established. It is the burial place of the Prophet, whose tomb lies beneath the green dome of Al-Masjid an-Nabawi, the Prophet's Mosque, expanded over fourteen centuries from a simple palm-trunk enclosure into one of the largest mosques on earth. The first two caliphs, Abu Bakr and Umar, are buried alongside him; the nearby Quba Mosque is traditionally identified as the first mosque built in Islam. Medina's classical role as the cradle of the early Muslim community, the codification of prophetic Sunnah, and the formation of the Maliki legal school still shapes its religious life today, where pilgrims combine visits to the Rawdah with study circles in the Haram and the city retains a deeply observant, scholarly character.