Which Assassin's Creed game first introduced the Brotherhood headquarters in Monteriggioni?

Assassin's Creed II first introduced the Brotherhood headquarters in Monteriggioni.

Monteriggioni is the Tuscan town where Ezio Auditore's family villa becomes a base for his activities. After reaching the villa, Ezio and his allies restore parts of the estate, recruit support, and use the location as a safe center between missions across Renaissance Italy.

The town was introduced in Assassin's Creed II, released in 2009. It returns prominently in Assassin's Creed Brotherhood, where the consequences of a Templar attack make its defense and recovery important to the story. That sequel's title can therefore lead players to remember Monteriggioni primarily from Brotherhood.

Monteriggioni is a real medieval walled town in Tuscany, although the game adapts its geography and architecture for gameplay. It should not be confused with Villa Auditore itself, which is the central estate inside the town.