A Muslim object of veneration built into the eastern-facing corner of the Caaba. It predates the Islamic religion and is probably of meteoric origin although according to Islamic legend the stone was given to Adam on his fall from paradise (however some conflicting legends say it was given to Abraham and Ishmael from an angel of heaven). It currently consists of several fragments held together with a silver band and surrounded by a stone ring. It's not worshipped as holy per se and is often used as a starting point when pilgrims circle the Caaba during the hajj. It is also, as rk2001 notes, called the "Hajr-el-Aswad".