Two things are a must when visiting Rio. First, is to make one's way up Corcovado Mountain to the the tatue of Christ the Redeamer. This offers truly awesome scenic vantages of the surrounding city including Copacabana and Ipanema, Centro, and the gigantic Maracana soccer stadum (the largest in the world). On the main road up the mountain you pass by (not through) an authentic favela, as well as lush green spaces.
The second is the aerial tram ride to the top of Sugar Loaf Mountain to experience the beautiful views of coastal Rio.
Quick Tips:
Historically, Rio has had a very bad reputation as a violent city plagued with petty crime, muggings, and indeed plenty of armed robberies. However, I experienced absolutely no problems during my weeklong stay.
Public buses were clean, and the conductors very helpful. Taxis were safe, inexpensive, and the drivers also very helpful. The beaches were lively, with people out and about at all hours. Now that the beaches (Copacabana and Ipanema) are floodlit at night,there is perportedly a lot less crime there.
It is important though to exercise common sense and to take basic safety measures. The key is to the local scene as much as possible to avoid hassles and rip offs. Also, there are certain parts of the city that no tourist belongs, including the favelas and the Copacabana Beach late at night when the prostitutes and johns are out and about.
Best Way To Get Around:
Copacabana and Ipanema are fairly easy to navigate on foot. Public buses from these areas to Centro and the gigantic Rio Sul shopping center in Gloria are plentiful and easy to spot. Taxis are inexpensive and good for rides late at night, or to areas further afield. like downtown. The cheapest way from the airport to any of the hotels in Copacabana or Ipanema is by way of a Real bus. They depart the airport every half hour and will stop at most hotels in these areas. To catch a bus back to the airport simply hail them along Copacabana or Ipanema beach, and they'll stop.