Antico Teatro Romano
The Antico Teatro Romano (Italian: Ancient Roman Theatre) is an ancient Amphitheatre just outside San Gimignano and is a location in Assassin's Creed II. It appears prominently in the mission 'With Friends like These,' when Ezio must follow Jacopo de' Pazzi to a Templar meeting located in the Theatre. The Theatre is not, as it's name suggests, Roman, but is in fact Etruscan. There is a glyph here on the northern wing of seats.
In its day, the Theatre was built of concrete decorated with marble columns, but by Ezio's time, all the marble had been pilfered by looters and the recipe for concrete was lost with the fall of Rome. Renaissance Italians practiced a rudimentary form of recycling building materials. Any marble that could be found in old Roman buildings were torn out and reused in more modern structures.