In the original Assassin's Creed game, Altaïr's home base during much of the story is Masyaf.
Masyaf is a mountain settlement in modern-day Syria and the headquarters of the Assassin Brotherhood led by Al Mualim. Altaïr returns there between major missions to receive instructions, report his progress, and obtain new equipment or abilities. The settlement also serves as the opening and closing location for much of the game's main narrative.
The game places Masyaf in the Levant during the Third Crusade, alongside historical cities including Jerusalem, Acre, and Damascus. These cities are major mission locations, which can make them easy to confuse with Altaïr's headquarters. Masyaf is distinct because it is the Brotherhood's fortified base rather than one of the principal assassination districts.
The game's version draws on the historical association between Masyaf and the Nizari Ismaili community, often called the Assassins in popular Western writing. Its fictionalized setting combines that historical backdrop with the series' science-fiction framework.