Everyone knows this famous square: not surprisingly, it is the main one! Get there and start looking. It is huge: will you be able to find the QR code and discover the code that will take you to the next stop?
Before you start looking, though, here's the next challenge: Tourists! Find tourists and take a mega photo all together-the more people there are, the more points you will receive.
Remember to upload it!
Mind you, tourists will have to be aware-and smile!