The Piazza Cafe comes with the special set bonus. When it is adjacent to other buildings belonging to the Piazza Set the properties of the building are improved.
The Piazza Cafe can be upgraded by Piazza Cafe Upgrade Kit item. To upgrade the Piazza Cafe, use the Piazza Cafe Upgrade item on the Piazza Cafe that is already situated in your city. Its upgraded version will then be placed directly on the same spot in your city and the production timer will not be reset. Note that the upgraded building will be from your current era, even if the old one was from one of the earlier ages.
Piazza Cafe will produce the following effects. Base effects will always be produced. Bonus effects are determined by how many other unique Piazza Set buildings it is connected to.