Assassin's Creed: Brotherhood

You can get this early in sequence 3. There is a memory available in the southwest at the start of the sequence. This memory is for La Volpe. At the end of this memory you with need to approach an architect to upgrade the Thieves building. This counts towards the trophy. In the area are a blacksmith, horse stable, doctor, and an art merchant. Get all of these and you'll get the trophy. The 4 buildings not tied directly to the memory can be upgraded prior to starting the memory, though they are easier to find after completing the memory to get the viewpoint to synch with to reveal their locations.