Another plaza right by the basilica. Full of people selling stuff as well.
There are tons of people selling stuff here, but it isn't as crowded as the front of the basilica.
It is very expensive just for the basic tickets, but it is quite beautiful inside. Lines to get in are long so buy your tickets online. Expect security that is tighter than security at the airport
I would spend at least 5 days here to explore all that this city has to offer.