If you have a passion for art and architecture head for downtown Rio. The best time to walk around is between April and November, before it gets too hot. You can started at Centro Cultural Banco do Brasil (they usually have superb exhibitions there) and just walk to Paço Imperial, stopping along the way at Casa França Brasil and Espaço Cultural dos Correios. There are wonderful restaurants in the area, including the one at Casa França Brasil, the Bistrô Rosário, and Cais do Oriente, to name just a few. When the Museu Nacional de Belas Artes reopens after extensive renovations, it should become another top destination for art lovers. The gorgeous Museu Histórico Nacional and the Museu de Arte Moderna (MAM) with its Burle Marx gardens are not too far apart and can be probably combined in one day.
Another great excursion is to catch the bondinho or tram that goes over the old acqueduct and up to Santa Teresa, what a thrill that is! Once there, walk around for the views and all the old homes. Fantastic restaurants abound, too, such as Bar do Mineiro, Adega do Pimenta, Bar do Arnaudo, Aprazível, Asia, Sobrenatural (which incorporated junked tram parts into its walls), etc.
Here are some photos I've taken over the years. Enjoy and keep coming for more; we have every intention of going back many, many times!