Assassin's Creed II

You first acquire the ability to renovate Monteriggioni at the beginning of DNA Sequence 4. After speaking with Claudia in the workshop in the villa, you need to speak with the architect standing in the same room. He will explain to you that renovating the entire town will take lots of money. You make a promise to him that he will get all the money he needs to bring the town and villa back to life. Once you have finished with the conversation, you will be looking at a model miniature of the town sitting on a table. Scroll through the different buildings to find out how much each costs to renovate. The Tailor or the first tier of the Art Merchant is the cheapest to renovate, each only costing 1,000ƒ. If you have enough money at this point, press to select the building you’ve chosen and the achievement will unlock. If not, return to the villa when you do and follow the same procedure.

Thanks to G4MERM4NIACO for the video: