Rio is a city filled with just about everything desirable and undesirable in a city of its size. The people are beautiful, the beaches are beautiful and the food is excellent and CHEAP.
The downside is that you really need to either stay in safe areas, or have some Brazilian friends if you really want to venture out. Luckily, I had met an exchange student in the U.S. before I travelled to Rio. Once I got there, he took me to all of the cool clubs, the best beaches that tourists don't know about, and restaurants off the beaten path. I never would have seen Rio this way if it was not for him!