In the original Assassin's Creed, Masyaf is the headquarters of the Assassin Order.
Masyaf is a fortified mountain settlement in Syria and serves as the Assassins' principal base under their mentor, Al Mualim. The game begins there before Altaïr Ibn-La'Ahad is sent on missions across the Holy Land.
The three main cities visited during the game are Damascus, Jerusalem, and Acre. They are mission locations, not the order's headquarters. Masyaf is therefore easy to confuse with the larger cities that dominate the game's map, but its role is different: it is the central training, political, and administrative home of the Assassins.