Downtown Rio

Feira do Lavradio - Lavradio's Fair: Antiques, Crafts, Bric-a-Brac, Music, Food, People, with colonial buildings along the street and neighborhood, but with a very modern cathedral nearby (Roman Catholic Church). 

Walk around:

Theatro Municipal: Praça Marechal Floriano (Subway: Cinelandia Station)

Gustavo Capanema Palace - Candido Portinari Tile Work (Av. Graça Aranha)
http://en.wikipedia.org/wiki/Candido_Portinari