Rabat's history began with a settlement, known as Chellah on the banks of the Oued Bou Regreg in the third century BC. In 40 AD, Romans took over Chellah and changed it to the Roman settlement of Sala Colonia. Rome held the colony until 250 AD. They gave it up to local rulers. In 1146, the berber Almohad ruler Abd al-Mu'min turned Rabat's ribat into a full scale fortress. It was used as a starting point for attacks on Spain. In 1170, due to its military importance, Rabat acquired the title "Ribatu l-Fath", meaning "stronghold of victory," from which it gets its current name.