In the original Assassin's Creed, the Assassin bureau headquarters is located in Masyaf.
Masyaf is the mountain fortress that serves as the main base of the Levantine Assassins in 1191. Altaïr Ibn-La'Ahad returns there repeatedly to receive missions, report to Al Mualim, and recover from assignments in the major cities of the Holy Land.
The fortress is based on the real town of Masyaf in modern Syria. Historically, Masyaf was associated with the Nizari Ismaili state, a community often linked in popular culture with the word “Assassin.” The game uses the location as both a political center and a training ground.
Players sometimes confuse Masyaf with the three cities where most assassination missions occur: Jerusalem, Acre, and Damascus. Those cities are mission locations, while Masyaf is the headquarters and starting point for the order’s operations.