Igreja São Francisco de Assis
Ouro Prêto is perhaps one of the prettiest places to visit in Brazil.  Nestled beautifully in a rolling valley, it is full of colonial churches, steep streets, and more artifacts to buy than you would know what to do with.  I stayed in a hotel right next to this church, on top of a hill, on a little square with a souvenir market on it (seems a lot of tourists make there way here).  This is one of the most important churches in Brazil, and was built by a fellow named Aleijadinho.