In the first Assassin's Creed game, Masyaf is home to the Assassin bureau where Altaïr begins.
Masyaf is a mountain settlement in present-day Syria and serves as the headquarters of the Assassin Brotherhood during the game's 1191 storyline. Altaïr returns there to report to Al Mualim, the Brotherhood's master, and receives assignments connected with the Third Crusade.
The game also sends Altaïr to three major cities: Jerusalem, Acre, and Damascus. Those cities are mission locations, but they are not the Brotherhood's headquarters. This distinction causes a common mix-up because much of the playable investigation takes place away from Masyaf.
Masyaf is based on a real Syrian town associated with the historical Nizari Ismaili community. Assassin's Creed combines that historical association with fictional characters, secret passages, and dramatic architecture to create its version of the Assassin stronghold.